Messages in this thread | | | Subject | Re: why nfs server delay 10ms in nfsd_write()? | From | Lee Revell <> | Date | Wed, 18 May 2005 23:13:43 -0400 |
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On Thu, 2005-05-19 at 10:46 +0800, steve wrote: > i have 2 questions: > 1.i don't know why do we have to sleep for 10 ms, why not do sync immediately? > 2.what will happen if we don't sleep for 10ms? > when i delete these codes, i get a good result, and the write performace improved from 300KB/s to 18MB/s >
Did you read the comments in the code?
/* * Gathered writes: If another process is currently * writing to the file, there's a high chance * this is another nfsd (triggered by a bulk write * from a client's biod). Rather than syncing the * file with each write request, we sleep for 10 msec. * * I don't know if this roughly approximates * C. Juszak's idea of gathered writes, but it's a * nice and simple solution (IMHO), and it seems to * work:-) */ if (EX_WGATHER(exp)) { if (atomic_read(&inode->i_writecount) > 1 || (last_ino == inode->i_ino && last_dev == inode->i_sb->s_dev)) { dprintk("nfsd: write defer %d\n", current->pid); msleep(10); dprintk("nfsd: write resume %d\n", current->pid); }
if (inode->i_state & I_DIRTY) { dprintk("nfsd: write sync %d\n", current->pid); nfsd_sync(file); } #if 0 wake_up(&inode->i_wait); #endif }
Lee
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