proc: meminfo: Replace kB with KiB in output
Subsystems (2)
Hi!
I was helping somebody write some documentation about meminfo and I started explaining that memory values are mostly multiples of 1024 and that binary prefixes are preferred. The output of /proc/meminfo is hardcoded to be in 'kB' which should mean 1000 bytes (one kilobytes). But judging by the definition of the K() macro it is based on page size which is a multiple of 1024. So the values are actually kibibytes (KiB). Therefore we got stuck with writing the documentation because there is a discrepancy between the output and the code.
If I am mistaken, please correct me and ignore the rest of the message.
I know there is a big debate about using binary prefixes versus using the de facto definitions based on powers of 10. The technically correct usage in this case would be KiB but I am thinking that nobody changed this because it might break things.
Therefore I am writing this email with the main purpose of finding out what is the reason what the output is as it is. Is it because changing it would break userspace tools that read /proc/meminfo ? Or is it because the technical correctness of the binary prefix side in the debate lost? Or just because nobody bothered fixing this?
If the last reason is the answer I would like to take the first step in addressing it with this RFC.
Thank you!
PATCH 1/1 proc: meminfo: Replace kB with KiB in output
Current values are based on multiples of 1024 (powers of 2) which means that the values in meminfo are not kilobytes (1000 bytes) but kibibytes (1024 bytes). The correct prefix for that would be 'Ki' so the output should be 'KiB'.
--- fs/proc/meminfo.c | 90 +++++++++++++++++++++++++++---------------------------- 1 file changed, 45 insertions(+), 45 deletions(-)
fs/proc/meminfo.c +45 -45
@@ -33,7 +33,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)int lru;/* -* display in kilobytes. +* display in kibibytes. */ #define K (x) ((x) << (PAGE_SHIFT - 10))si_meminfo (&i);
@@ -54,61 +54,61 @@ static int meminfo_proc_show(struct seq_file *m, void *v)* Tagged format, for easy grepping and expansion. */ seq_printf(m, - "MemTotal: %8lu kB\n" - "MemFree: %8lu kB\n" - "MemAvailable: %8lu kB\n" - "Buffers: %8lu kB\n" - "Cached: %8lu kB\n" - "SwapCached: %8lu kB\n" - "Active: %8lu kB\n" - "Inactive: %8lu kB\n" - "Active(anon): %8lu kB\n" - "Inactive(anon): %8lu kB\n" - "Active(file): %8lu kB\n" - "Inactive(file): %8lu kB\n" - "Unevictable: %8lu kB\n" - "Mlocked: %8lu kB\n" + "MemTotal: %8lu KiB\n" + "MemFree: %8lu KiB\n" + "MemAvailable: %8lu KiB\n" + "Buffers: %8lu KiB\n" + "Cached: %8lu KiB\n" + "SwapCached: %8lu KiB\n" + "Active: %8lu KiB\n" + "Inactive: %8lu KiB\n" + "Active(anon): %8lu KiB\n" + "Inactive(anon): %8lu KiB\n" + "Active(file): %8lu KiB\n" + "Inactive(file): %8lu KiB\n" + "Unevictable: %8lu KiB\n" + "Mlocked: %8lu KiB\n" #ifdef CONFIG_HIGHMEM - "HighTotal: %8lu kB\n" - "HighFree: %8lu kB\n" - "LowTotal: %8lu kB\n" - "LowFree: %8lu kB\n" + "HighTotal: %8lu KiB\n" + "HighFree: %8lu KiB\n" + "LowTotal: %8lu KiB\n" + "LowFree: %8lu KiB\n" #endif #ifndef CONFIG_MMU - "MmapCopy: %8lu kB\n" + "MmapCopy: %8lu KiB\n" #endif - "SwapTotal: %8lu kB\n" - "SwapFree: %8lu kB\n" - "Dirty: %8lu kB\n" - "Writeback: %8lu kB\n" - "AnonPages: %8lu kB\n" - "Mapped: %8lu kB\n" - "Shmem: %8lu kB\n" - "Slab: %8lu kB\n" - "SReclaimable: %8lu kB\n" - "SUnreclaim: %8lu kB\n" - "KernelStack: %8lu kB\n" - "PageTables: %8lu kB\n" + "SwapTotal: %8lu KiB\n" + "SwapFree: %8lu KiB\n" + "Dirty: %8lu KiB\n" + "Writeback: %8lu KiB\n" + "AnonPages: %8lu KiB\n" + "Mapped: %8lu KiB\n" + "Shmem: %8lu KiB\n" + "Slab: %8lu KiB\n" + "SReclaimable: %8lu KiB\n" + "SUnreclaim: %8lu KiB\n" + "KernelStack: %8lu KiB\n" + "PageTables: %8lu KiB\n" #ifdef CONFIG_QUICKLIST - "Quicklists: %8lu kB\n" + "Quicklists: %8lu KiB\n" #endif - "NFS_Unstable: %8lu kB\n" - "Bounce: %8lu kB\n" - "WritebackTmp: %8lu kB\n" - "CommitLimit: %8lu kB\n" - "Committed_AS: %8lu kB\n" - "VmallocTotal: %8lu kB\n" - "VmallocUsed: %8lu kB\n" - "VmallocChunk: %8lu kB\n" + "NFS_Unstable: %8lu KiB\n" + "Bounce: %8lu KiB\n" + "WritebackTmp: %8lu KiB\n" + "CommitLimit: %8lu KiB\n" + "Committed_AS: %8lu KiB\n" + "VmallocTotal: %8lu KiB\n" + "VmallocUsed: %8lu KiB\n" + "VmallocChunk: %8lu KiB\n" #ifdef CONFIG_MEMORY_FAILURE - "HardwareCorrupted: %5lu kB\n" + "HardwareCorrupted: %5lu KiB\n" #endif #ifdef CONFIG_TRANSPARENT_HUGEPAGE - "AnonHugePages: %8lu kB\n" + "AnonHugePages: %8lu KiB\n" #endif #ifdef CONFIG_CMA - "CmaTotal: %8lu kB\n" - "CmaFree: %8lu kB\n" + "CmaTotal: %8lu KiB\n" + "CmaFree: %8lu KiB\n" #endif , K(i.totalram),
Signature · 1 line
2.5.5
Quoted 4 lines · Alexandru Juncu
Current values are based on multiples of 1024 (powers of 2) which means that the values in meminfo are not kilobytes (1000 bytes) but kibibytes (1024 bytes). The correct prefix for that would be 'Ki' so the output should be 'KiB'.
Does the difference actually matters so much that we should change a user visible format of a file? Some users might not ready to changes (say sombody did sed 's@.*:[[:space:]]*\([0-9]*\) kB@\1@' to get values. This change would break it which is something we try to prevent as much as possible.
So I do not think this all is worth the potential troubles. There are probably other places where we present kB while we in fact think kiB.
Quoted 127 lines
Signed-off-by Alexandru Juncu <[email protected]>--- fs/proc/meminfo.c | 90 +++++++++++++++++++++++++++---------------------------- 1 file changed, 45 insertions(+), 45 deletions(-)fs/proc/meminfo.c +45
-45@@ -33,7 +33,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)int lru;/* -* display in kilobytes. +* display in kibibytes. */ #define K (x) ((x) << (PAGE_SHIFT - 10))si_meminfo (&i);@@ -54,61 +54,61 @@ static int meminfo_proc_show(struct seq_file *m, void *v)* Tagged format, for easy grepping and expansion. */ seq_printf(m, - "MemTotal: %8lu kB\n" - "MemFree: %8lu kB\n" - "MemAvailable: %8lu kB\n" - "Buffers: %8lu kB\n" - "Cached: %8lu kB\n" - "SwapCached: %8lu kB\n" - "Active: %8lu kB\n" - "Inactive: %8lu kB\n" - "Active(anon): %8lu kB\n" - "Inactive(anon): %8lu kB\n" - "Active(file): %8lu kB\n" - "Inactive(file): %8lu kB\n" - "Unevictable: %8lu kB\n" - "Mlocked: %8lu kB\n" + "MemTotal: %8lu KiB\n" + "MemFree: %8lu KiB\n" + "MemAvailable: %8lu KiB\n" + "Buffers: %8lu KiB\n" + "Cached: %8lu KiB\n" + "SwapCached: %8lu KiB\n" + "Active: %8lu KiB\n" + "Inactive: %8lu KiB\n" + "Active(anon): %8lu KiB\n" + "Inactive(anon): %8lu KiB\n" + "Active(file): %8lu KiB\n" + "Inactive(file): %8lu KiB\n" + "Unevictable: %8lu KiB\n" + "Mlocked: %8lu KiB\n" #ifdef CONFIG_HIGHMEM - "HighTotal: %8lu kB\n" - "HighFree: %8lu kB\n" - "LowTotal: %8lu kB\n" - "LowFree: %8lu kB\n" + "HighTotal: %8lu KiB\n" + "HighFree: %8lu KiB\n" + "LowTotal: %8lu KiB\n" + "LowFree: %8lu KiB\n" #endif #ifndef CONFIG_MMU - "MmapCopy: %8lu kB\n" + "MmapCopy: %8lu KiB\n" #endif - "SwapTotal: %8lu kB\n" - "SwapFree: %8lu kB\n" - "Dirty: %8lu kB\n" - "Writeback: %8lu kB\n" - "AnonPages: %8lu kB\n" - "Mapped: %8lu kB\n" - "Shmem: %8lu kB\n" - "Slab: %8lu kB\n" - "SReclaimable: %8lu kB\n" - "SUnreclaim: %8lu kB\n" - "KernelStack: %8lu kB\n" - "PageTables: %8lu kB\n" + "SwapTotal: %8lu KiB\n" + "SwapFree: %8lu KiB\n" + "Dirty: %8lu KiB\n" + "Writeback: %8lu KiB\n" + "AnonPages: %8lu KiB\n" + "Mapped: %8lu KiB\n" + "Shmem: %8lu KiB\n" + "Slab: %8lu KiB\n" + "SReclaimable: %8lu KiB\n" + "SUnreclaim: %8lu KiB\n" + "KernelStack: %8lu KiB\n" + "PageTables: %8lu KiB\n" #ifdef CONFIG_QUICKLIST - "Quicklists: %8lu kB\n" + "Quicklists: %8lu KiB\n" #endif - "NFS_Unstable: %8lu kB\n" - "Bounce: %8lu kB\n" - "WritebackTmp: %8lu kB\n" - "CommitLimit: %8lu kB\n" - "Committed_AS: %8lu kB\n" - "VmallocTotal: %8lu kB\n" - "VmallocUsed: %8lu kB\n" - "VmallocChunk: %8lu kB\n" + "NFS_Unstable: %8lu KiB\n" + "Bounce: %8lu KiB\n" + "WritebackTmp: %8lu KiB\n" + "CommitLimit: %8lu KiB\n" + "Committed_AS: %8lu KiB\n" + "VmallocTotal: %8lu KiB\n" + "VmallocUsed: %8lu KiB\n" + "VmallocChunk: %8lu KiB\n" #ifdef CONFIG_MEMORY_FAILURE - "HardwareCorrupted: %5lu kB\n" + "HardwareCorrupted: %5lu KiB\n" #endif #ifdef CONFIG_TRANSPARENT_HUGEPAGE - "AnonHugePages: %8lu kB\n" + "AnonHugePages: %8lu KiB\n" #endif #ifdef CONFIG_CMA - "CmaTotal: %8lu kB\n" - "CmaFree: %8lu kB\n" + "CmaTotal: %8lu KiB\n" + "CmaFree: %8lu KiB\n" #endif , K(i.totalram),Signature · 1 line
2.5.5
Signature · 2 lines
Michal Hocko SUSE Labs
Quoted 6 lines · Michal Hocko
Quoted 4 lines · Alexandru Juncu
Current values are based on multiples of 1024 (powers of 2) which means that the values in meminfo are not kilobytes (1000 bytes) but kibibytes (1024 bytes). The correct prefix for that would be 'Ki' so the output should be 'KiB'.
Quoted 8 lines
Does the difference actually matters so much that we should change a user visible format of a file? Some users might not ready to changes (say sombody did sed 's@.*:[[:space:]]*\([0-9]*\) kB@\1@' to get values. This change would break it which is something we try to prevent as much as possible.
So I do not think this all is worth the potential troubles. There are probably other places where we present kB while we in fact think kiB.
Isn't it at least worth clearly specifying this in the documentation (maybe also comment in code)?
Quoted 132 lines
Quoted 126 lines
Signed-off-by Alexandru Juncu <[email protected]>--- fs/proc/meminfo.c | 90 +++++++++++++++++++++++++++---------------------------- 1 file changed, 45 insertions(+), 45 deletions(-)fs/proc/meminfo.c +45
-46@@ -33,7 +33,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)int lru;/* -* display in kilobytes. +* display in kibibytes. */ #define K (x) ((x) << (PAGE_SHIFT - 10))si_meminfo (&i);@@ -54,61 +54,61 @@ static int meminfo_proc_show(struct seq_file *m, void *v)* Tagged format, for easy grepping and expansion. */ seq_printf(m, - "MemTotal: %8lu kB\n" - "MemFree: %8lu kB\n" - "MemAvailable: %8lu kB\n" - "Buffers: %8lu kB\n" - "Cached: %8lu kB\n" - "SwapCached: %8lu kB\n" - "Active: %8lu kB\n" - "Inactive: %8lu kB\n" - "Active(anon): %8lu kB\n" - "Inactive(anon): %8lu kB\n" - "Active(file): %8lu kB\n" - "Inactive(file): %8lu kB\n" - "Unevictable: %8lu kB\n" - "Mlocked: %8lu kB\n" + "MemTotal: %8lu KiB\n" + "MemFree: %8lu KiB\n" + "MemAvailable: %8lu KiB\n" + "Buffers: %8lu KiB\n" + "Cached: %8lu KiB\n" + "SwapCached: %8lu KiB\n" + "Active: %8lu KiB\n" + "Inactive: %8lu KiB\n" + "Active(anon): %8lu KiB\n" + "Inactive(anon): %8lu KiB\n" + "Active(file): %8lu KiB\n" + "Inactive(file): %8lu KiB\n" + "Unevictable: %8lu KiB\n" + "Mlocked: %8lu KiB\n" #ifdef CONFIG_HIGHMEM - "HighTotal: %8lu kB\n" - "HighFree: %8lu kB\n" - "LowTotal: %8lu kB\n" - "LowFree: %8lu kB\n" + "HighTotal: %8lu KiB\n" + "HighFree: %8lu KiB\n" + "LowTotal: %8lu KiB\n" + "LowFree: %8lu KiB\n" #endif #ifndef CONFIG_MMU - "MmapCopy: %8lu kB\n" + "MmapCopy: %8lu KiB\n" #endif - "SwapTotal: %8lu kB\n" - "SwapFree: %8lu kB\n" - "Dirty: %8lu kB\n" - "Writeback: %8lu kB\n" - "AnonPages: %8lu kB\n" - "Mapped: %8lu kB\n" - "Shmem: %8lu kB\n" - "Slab: %8lu kB\n" - "SReclaimable: %8lu kB\n" - "SUnreclaim: %8lu kB\n" - "KernelStack: %8lu kB\n" - "PageTables: %8lu kB\n" + "SwapTotal: %8lu KiB\n" + "SwapFree: %8lu KiB\n" + "Dirty: %8lu KiB\n" + "Writeback: %8lu KiB\n" + "AnonPages: %8lu KiB\n" + "Mapped: %8lu KiB\n" + "Shmem: %8lu KiB\n" + "Slab: %8lu KiB\n" + "SReclaimable: %8lu KiB\n" + "SUnreclaim: %8lu KiB\n" + "KernelStack: %8lu KiB\n" + "PageTables: %8lu KiB\n" #ifdef CONFIG_QUICKLIST - "Quicklists: %8lu kB\n" + "Quicklists: %8lu KiB\n" #endif - "NFS_Unstable: %8lu kB\n" - "Bounce: %8lu kB\n" - "WritebackTmp: %8lu kB\n" - "CommitLimit: %8lu kB\n" - "Committed_AS: %8lu kB\n" - "VmallocTotal: %8lu kB\n" - "VmallocUsed: %8lu kB\n" - "VmallocChunk: %8lu kB\n" + "NFS_Unstable: %8lu KiB\n" + "Bounce: %8lu KiB\n" + "WritebackTmp: %8lu KiB\n" + "CommitLimit: %8lu KiB\n" + "Committed_AS: %8lu KiB\n" + "VmallocTotal: %8lu KiB\n" + "VmallocUsed: %8lu KiB\n" + "VmallocChunk: %8lu KiB\n" #ifdef CONFIG_MEMORY_FAILURE - "HardwareCorrupted: %5lu kB\n" + "HardwareCorrupted: %5lu KiB\n" #endif #ifdef CONFIG_TRANSPARENT_HUGEPAGE - "AnonHugePages: %8lu kB\n" + "AnonHugePages: %8lu KiB\n" #endif #ifdef CONFIG_CMA - "CmaTotal: %8lu kB\n" - "CmaFree: %8lu kB\n" + "CmaTotal: %8lu KiB\n" + "CmaFree: %8lu KiB\n" #endif , K(i.totalram), --Quoted 2 lines
2.5.5
--
Michal Hocko
SUSE Labs
Quoted 13 lines · Alexandru Juncu
Quoted 12 lines · Michal Hocko
Quoted 4 lines · Alexandru Juncu
Current values are based on multiples of 1024 (powers of 2) which means that the values in meminfo are not kilobytes (1000 bytes) but kibibytes (1024 bytes). The correct prefix for that would be 'Ki' so the output should be 'KiB'.
Does the difference actually matters so much that we should change a user visible format of a file? Some users might not ready to changes (say sombody did sed 's@.*:[[:space:]]*\([0-9]*\) kB@\1@' to get values. This change would break it which is something we try to prevent as much as possible.
Quoted 5 lines
Quoted 2 lines
So I do not think this all is worth the potential troubles. There are probably other places where we present kB while we in fact think kiB.
Isn't it at least worth clearly specifying this in the documentation (maybe also comment in code)?
Sure, improving our documentation is highly appreciated of course.
Thanks!
Signature · 2 lines
Michal Hocko SUSE Labs
Quoted 4 lines · Alexandru Juncu
Current values are based on multiples of 1024 (powers of 2) which means that the values in meminfo are not kilobytes (1000 bytes) but kibibytes (1024 bytes). The correct prefix for that would be 'Ki' so the output should be 'KiB'.
I'm pretty sure you will get NAK for that.
Obvious reason — procfs is ABI of the kernel. "We won't break userspace."
Quoted 128 lines
Signed-off-by Alexandru Juncu <[email protected]>--- fs/proc/meminfo.c | 90 +++++++++++++++++++++++++++---------------------------- 1 file changed, 45 insertions(+), 45 deletions(-)fs/proc/meminfo.c +45
-46@@ -33,7 +33,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)int lru;/* -* display in kilobytes. +* display in kibibytes. */ #define K (x) ((x) << (PAGE_SHIFT - 10))si_meminfo (&i);@@ -54,61 +54,61 @@ static int meminfo_proc_show(struct seq_file *m, void *v)* Tagged format, for easy grepping and expansion. */ seq_printf(m, - "MemTotal: %8lu kB\n" - "MemFree: %8lu kB\n" - "MemAvailable: %8lu kB\n" - "Buffers: %8lu kB\n" - "Cached: %8lu kB\n" - "SwapCached: %8lu kB\n" - "Active: %8lu kB\n" - "Inactive: %8lu kB\n" - "Active(anon): %8lu kB\n" - "Inactive(anon): %8lu kB\n" - "Active(file): %8lu kB\n" - "Inactive(file): %8lu kB\n" - "Unevictable: %8lu kB\n" - "Mlocked: %8lu kB\n" + "MemTotal: %8lu KiB\n" + "MemFree: %8lu KiB\n" + "MemAvailable: %8lu KiB\n" + "Buffers: %8lu KiB\n" + "Cached: %8lu KiB\n" + "SwapCached: %8lu KiB\n" + "Active: %8lu KiB\n" + "Inactive: %8lu KiB\n" + "Active(anon): %8lu KiB\n" + "Inactive(anon): %8lu KiB\n" + "Active(file): %8lu KiB\n" + "Inactive(file): %8lu KiB\n" + "Unevictable: %8lu KiB\n" + "Mlocked: %8lu KiB\n" #ifdef CONFIG_HIGHMEM - "HighTotal: %8lu kB\n" - "HighFree: %8lu kB\n" - "LowTotal: %8lu kB\n" - "LowFree: %8lu kB\n" + "HighTotal: %8lu KiB\n" + "HighFree: %8lu KiB\n" + "LowTotal: %8lu KiB\n" + "LowFree: %8lu KiB\n" #endif #ifndef CONFIG_MMU - "MmapCopy: %8lu kB\n" + "MmapCopy: %8lu KiB\n" #endif - "SwapTotal: %8lu kB\n" - "SwapFree: %8lu kB\n" - "Dirty: %8lu kB\n" - "Writeback: %8lu kB\n" - "AnonPages: %8lu kB\n" - "Mapped: %8lu kB\n" - "Shmem: %8lu kB\n" - "Slab: %8lu kB\n" - "SReclaimable: %8lu kB\n" - "SUnreclaim: %8lu kB\n" - "KernelStack: %8lu kB\n" - "PageTables: %8lu kB\n" + "SwapTotal: %8lu KiB\n" + "SwapFree: %8lu KiB\n" + "Dirty: %8lu KiB\n" + "Writeback: %8lu KiB\n" + "AnonPages: %8lu KiB\n" + "Mapped: %8lu KiB\n" + "Shmem: %8lu KiB\n" + "Slab: %8lu KiB\n" + "SReclaimable: %8lu KiB\n" + "SUnreclaim: %8lu KiB\n" + "KernelStack: %8lu KiB\n" + "PageTables: %8lu KiB\n" #ifdef CONFIG_QUICKLIST - "Quicklists: %8lu kB\n" + "Quicklists: %8lu KiB\n" #endif - "NFS_Unstable: %8lu kB\n" - "Bounce: %8lu kB\n" - "WritebackTmp: %8lu kB\n" - "CommitLimit: %8lu kB\n" - "Committed_AS: %8lu kB\n" - "VmallocTotal: %8lu kB\n" - "VmallocUsed: %8lu kB\n" - "VmallocChunk: %8lu kB\n" + "NFS_Unstable: %8lu KiB\n" + "Bounce: %8lu KiB\n" + "WritebackTmp: %8lu KiB\n" + "CommitLimit: %8lu KiB\n" + "Committed_AS: %8lu KiB\n" + "VmallocTotal: %8lu KiB\n" + "VmallocUsed: %8lu KiB\n" + "VmallocChunk: %8lu KiB\n" #ifdef CONFIG_MEMORY_FAILURE - "HardwareCorrupted: %5lu kB\n" + "HardwareCorrupted: %5lu KiB\n" #endif #ifdef CONFIG_TRANSPARENT_HUGEPAGE - "AnonHugePages: %8lu kB\n" + "AnonHugePages: %8lu KiB\n" #endif #ifdef CONFIG_CMA - "CmaTotal: %8lu kB\n" - "CmaFree: %8lu kB\n" + "CmaTotal: %8lu KiB\n" + "CmaFree: %8lu KiB\n" #endif , K(i.totalram), --2.5.5
Signature · 2 lines
With Best Regards, Andy Shevchenko