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On 10/14/10 12:04 AM, Jeremy Filizetti wrote:
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cite="mid:AANLkTikAwYzfEMbSzE5Yhpj5KrbwMhTjV7dqtWQNBwH6@mail.gmail.com"
type="cite">
<div>I've put together a small patch to modify ll_dir_readpage and
mdc_readpage to read extra pages (if available) with each RPC.
It is posted under the bug (<a moz-do-not-send="true"
href="https://bugzilla.lustre.org/show_bug.cgi?id=17833">https://bugzilla.lustre.org/show_bug.cgi?id=17833</a>).
I see you we're the original assignee when you were at
Sun/Oracle.</div>
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Thanks, I will study such patch. I added Lsy into such bug CC list
who is interested in it also.<br>
<br>
--<br>
Nasf<br>
<blockquote
cite="mid:AANLkTikAwYzfEMbSzE5Yhpj5KrbwMhTjV7dqtWQNBwH6@mail.gmail.com"
type="cite">
<div> </div>
<div>Jeremy<br>
<br>
</div>
<div class="gmail_quote">2010/9/29 Fan Yong <span dir="ltr"><<a
moz-do-not-send="true" href="mailto:yong.fan@whamcloud.com">yong.fan@whamcloud.com</a>></span><br>
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<div class="h5">On 9/30/10 3:01 AM, Jeremy Filizetti
wrote:
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On the other hand, Large readdir RPCs is basic
of another metadata read performance improvement
features - "readdir+", which is quite useful for
"ls -l" operation (for large directory), and
reduce lookup/getattr RPC as much as possible.
In such feature, MDS will pack more dir-item's
attribute (not only name/ino as does currently
by readdir, but also mode/owner, and etc)
information back to client-side in "readdir+"
RPC. That means the dir-item count in one
"readdir+" page is less than in the traditional
readdir page, then more pages to be sent back to
client. If without "Large readdir RPCs", the
advantage of "readdir+" will be discounted.<br>
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<div> </div>
<div>I'd be interested in working this as well but
probably as a separate effort since SOM isn't in
1.8 and that's my main focus. In our testing, SOM
had significant benefits over the WAN and I'd
expect even better from readdir+. I have tried
Oleg's patch for asynchronous ll_glimpse_size but
oddly I've seen someone erradic performance where
at times it was worse then statahead and
synchronous ll_glimpse_size.</div>
<div> </div>
<div>Jeremy</div>
<div> </div>
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Yes, SOM is another important feature for metadata reading
performance improvement by bypassing the glimpse RPC between
client and OSS. Engineers from Lustre Group worked for that
for some time, hope can be released soon.<br>
<br>
As for the asynchronous ll_glimpse_size maybe cause bad
performance occasionally, one possible reason is that:
glimpse RPC maybe not obtain extent lock(s) if some others
in using such lock(s), so the file size information obtained
by asynchronous glimpse is invalid when it is really used
later, means the caller ("stat") has to send synchronous
glimpse again. Anyway, I did not study such patch, so it is
just a guess.<br>
<br>
<br>
Cheers,<br>
Nasf<br>
</div>
<br>
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