pnfs: Add per-LD-info to nfs_pageio_descriptor
Subsystems (2)
RFC 1/1 pnfs: Add per-LD-info to nfs_pageio_descriptor
What do you guys think? would it be acceptable to add a per-layout private-data to nfs_pageio_descriptor?
In obj-LD we have bunch of constrains on the size of the IO that involves some 64bit divisions, and math. These calculations are only needed to be preformed once when the offset of the first page is known. Then a simple wb_bytes can cache the results for subsequent calls. (And cannot be calculated before we know the IO's offset)
Also I might want to allocate the io_state earlier at the insert of the first page instead of at the actual call to write/read_pagelist, again, for the same reason above.
Today we get by because at the very end, if some constraints hit and not the full IO was preformed then we only set r/wdata->res.count to less then what was requested and these pages that are outside of the IOed range get to be read/written as part of a future request. But this is sub-optimal because that is done only at read/write_done time. By then the contiguous pages were already submitted to requests and the few left-over pages get submitted as their own request. This causes a seeky, unaligned and additional small IOs which, if calculated for at coalesce time, would be spared. With the up coming raid5/6 code this can cost dearly. (A single simple large contiguous IO becomes bunch of read-modify-write IOs)
I can see that also at filelayout_pg_test there are two 64bit divisions preformed on every page insert which could be optimized to a simple compare.
[BTW: Perhaps change the .write/read_pagelist() API to directly receive
the nfs_pageio_descriptor and avoid all the duplication of types and members copy
]
I'm making pg_ld_private as a "long" because a long is good for a pointer as well as an integer.
---
include/linux/nfs_page.h +1 -0
@@ -77,6 +77,7 @@ struct nfs_pageio_descriptor {int pg_error;const struct rpc_call_ops *pg_rpc_callops;struct pnfs_layout_segment *pg_lseg; +long pg_ld_private; };#define NFS_WBACK_BUSY (req) (test_bit(PG_BUSY,&(req)->wb_flags))
Quoted 30 lines · Boaz Harrosh
What do you guys think? would it be acceptable to add a per-layout private-data to
nfs_pageio_descriptor?In obj-LD we have bunch of constrains on the size of the IO that involves some 64bit divisions, and math. These calculations are only needed to be preformed once when the offset of the first page is known. Then a simple
wb_bytescan cache the results for subsequent calls. (And cannot be calculated before we know the IO's offset)Also I might want to allocate the
io_stateearlier at the insert of the first page instead of at the actual call to write/read_pagelist, again, for the same reason above.Today we get by because at the very end, if some constraints hit and not the full IO was preformed then we only set r/wdata->res.count to less then what was requested and these pages that are outside of the IOed range get to be read/written as part of a future request. But this is sub-optimal because that is done only at read/write_done time. By then the contiguous pages were already submitted to requests and the few left-over pages get submitted as their own request. This causes a seeky, unaligned and additional small IOs which, if calculated for at coalesce time, would be spared. With the up coming raid5/6 code this can cost dearly. (A single simple large contiguous IO becomes bunch of read-modify-write IOs)
I can see that also at
filelayout_pg_testthere are two 64bit divisions preformed on every page insert which could be optimized to a simple compare.
Quoted 7 lines
[BTW: Perhaps change the .write/read_pagelist() API to directly receive
thenfs_pageio_descriptorand avoid all the duplication of types and members copy
]I'm making
pg_ld_privateas a "long" because a long is good for a pointer as well as an integer.
I really prefer it to be a void * rather than long for the same reason just as used in practically every other place.
Benny
Quoted 20 lines
Signed-off-by Boaz Harrosh <[email protected]>---
include/linux/nfs_page.h +1
-1@@ -77,6 +77,7 @@ struct nfs_pageio_descriptor {int pg_error;const struct rpc_call_ops *pg_rpc_callops;struct pnfs_layout_segment *pg_lseg; +long pg_ld_private; };#define NFS_WBACK_BUSY (req) (test_bit(PG_BUSY,&(req)->wb_flags)) --To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to [email protected]
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