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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