Rename BTRfs to MuchSlowerFS ?
Quoted 3 lines
That's because dpkg is known for using (f)sync very heavily. btrfs
honours the sync request in all cases, so it's much much slower than ext3, which doesn't.
Hmm, is it really the case with ext3/ext4 (ignoring fsync in some cases)?
Sounds like a bug in ext3/ext4 then.
Is it documented anywhere where ext3/ext4 would just silently ignore fsync?
Signature · 2 lines
Tomasz Chmielewski http://wpkg.org
Quoted 9 lines · Tomasz Chmielewski
Quoted 3 lines
That's because dpkg is known for using (f)sync very heavily. btrfs
honours the sync request in all cases, so it's much much slower than ext3, which doesn't.Hmm, is it really the case with ext3/ext4 (ignoring fsync in some cases)?
Sounds like a bug in ext3/ext4 then.
Is it documented anywhere where ext3/ext4 would just silently ignore fsync?
They don't. Unteil recently ext3 and reiserfs would not flush the disk caches unless enabled by a mount option, but even that has recently been fixed.
Quoted 7 lines · Christoph Hellwig
Quoted 6 lines · Tomasz Chmielewski
Quoted 3 lines
That's because dpkg is known for using (f)sync very heavily. btrfs
honours the sync request in all cases, so it's much much slower than ext3, which doesn't.Hmm, is it really the case with ext3/ext4 (ignoring fsync in some cases)?
Quoted 7 lines
Quoted 3 lines
Sounds like a bug in ext3/ext4 then.
Is it documented anywhere where ext3/ext4 would just silently ignore fsync?
They don't. Unteil recently ext3 and reiserfs would not flush the disk caches unless enabled by a mount option, but even that has recently been fixed.
Apologies for disseminating my misunderstanding, then.
Hugo.
Signature · 4 lines
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
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--- You can get more with a kind word and a two-by-four than you ---
can with just a kind word. Quoted 12 lines · Hugo Mills
Quoted 11 lines · Christoph Hellwig
Quoted 9 lines · Tomasz Chmielewski
Quoted 3 lines
That's because dpkg is known for using (f)sync very heavily. btrfs
honours the sync request in all cases, so it's much much slower than ext3, which doesn't.Hmm, is it really the case with ext3/ext4 (ignoring fsync in some cases)?
Sounds like a bug in ext3/ext4 then.
Is it documented anywhere where ext3/ext4 would just silently ignore fsync?
Quoted 8 lines
Quoted 3 lines
They don't. Unteil recently ext3 and reiserfs would not flush the disk caches unless enabled by a mount option, but even that has recently been fixed.
Apologies for disseminating my misunderstanding, then.
Hugo.
I'm wondering if this may be the very same unacceptable behavior as discussed earlier also in the following message threads:
btrfs always writes something after sync news://news.gmane.org:119/CABVOS09hntXYUsCJBg+byEGC5y53j4DeT6b49Rx1AaRpqFV54A@mail.gmail.com
Re: Writes in idle/How to debug filesystem activity news://news.gmane.org:119/[email protected]
Re: Applications using fsync cause hangs for several seconds every few minutes
news://news.gmane.org:119/[email protected]
Btrfs slowdown news://news.gmane.org:119/CAO47_-9BLKWUGDEuzaLqHSq9tZkAUaO8FMQEy1pPk9A2Hb+5AQ@mail.gmail.com
PLEASE TEST: Everybody who is seeing weird and long hangs news://news.gmane.org:119/[email protected]
and this:
curious writes on mounted, not used btrfs filesystem
http://thread.gmane.org/gmane.comp.file-systems.btrfs/10840
and probably this:
2.6.37: Multi-second I/O latency while untarring
http://www.spinics.net/lists/linux-btrfs/msg08516.html
Hasn't the slowdown been fixed yet?
For those experiencing the slowdown issue btrfs is entirely useless... (I had to stop using btrfs because of these frequent slowdowns, while btrfs was doing most likely needless disk writes for multiple seconds, I couldn't work at all)
Can someone look into this if this is not fixed? There are numerous analysis reports in the above threads, without any constructive result.
Thanks