[OpenAFS] poor out of cache behavior on writing
Sven Oehme
oehmes@de.ibm.com
Tue, 18 Feb 2003 14:25:57 +0100
This is a multipart message in MIME format.
--=_alternative 0049C793C1256CD1_=
Content-Type: text/plain; charset="US-ASCII"
hy ,
yes i know , under aix it is not a Problem , but under Linux (Redhat 8.0
Kernel 2.4.18)
Sven
Paul Blackburn <mpb@est.ibm.com>
Sent by: openafs-info-admin@openafs.org
02/18/2003 01:47 PM
To: Sven Oehme/Germany/IBM@IBMDE
cc: Edward Moy <emoy@apple.com>, openafs-info@openafs.org,
openafs-info-admin@openafs.org
Subject: Re: [OpenAFS] poor out of cache behavior on
writing
Sven,
I have seen that using a 256mb RAM cache on a machine with 1gb RAM
running AIX did not crash.
--
cheers
paul http://acm.org/~mpb
Sven Oehme wrote:
>
> hy ,
>
> i have seen increasing the memcache size >50 mb on a Linux Server with
> 512 mb that afs is crashing .
>
> Sven
>
>
>
>
> *Paul Blackburn <mpb@est.ibm.com>*
> Sent by: openafs-info-admin@openafs.org
>
> 02/18/2003 10:06 AM
>
>
> To: Edward Moy <emoy@apple.com>
> cc: openafs-info@openafs.org
> Subject: Re: [OpenAFS] poor out of cache behavior on
> writing
>
>
>
>
>
> Edward Moy wrote:
>
> >
> > Yes, it is true that fast read performance should be a higher
> > priority. But if I want to read a 1 GB file from AFS, I have to write
> > it there in the first place.
> >
> > Look at the times to read that same 1 GB file:
> >
> > nfs 0.050u 18.050s 2:25.59 12.4%
> > afs 0.5GB cache 0.030u 10.300s 2:29.26 6.9%
> > afs 2GB cache 0.030u 11.250s 2:32.67 7.3%
> >
> > Within the normal fluctuations in the network itself, AFS is very
> > close to raw NFA, for first-time reading. But also note that even when
> > the cache is smaller than the file, one does not see the poor behavior
> > exhibited in the write case.
>
> Hi Edward,
>
> I think you have succintly made the point that you need to size
> your AFS cache appropriately for your workload.
>
> If you plan on working with 1gb files often and writing 1gb files
> into /afs/@cell/$whatever/ then you better configure a big enough AFS
> cache.
>
> I think that "cache thrashing" is similar to "page thrashing"
> in virtual memory operating systems. It is a situation that
> occurs when there is not enough resource allocated (eg cache too small)
> for the workload applied to it.
>
> Remember also that with AFS, you have a choice of disk cache
> or RAM cache. So if you have enough installed RAM, you
> will see faster access using AFS RAM cache (than using disk cache).
>
> >
> >
> > It takes 2 1/2 minutes to read the file, and 4 minutes to write it
> > when there is enough cache. But as a user, when that goes up to 10
> > minutes, and uses 80% of the processor, my first reaction would be
> > that something is wrong.
> >
> > From other comments I've seen, it appears that this is "expected"
> > (though hopefully not desirable) behavior. I just wanted to point out
> > that there is room for improvement in this area.
>
> You are absolutely right to point this out.
> If there is something "not working right" with AFS write function
> then this is a good place to discuss it and propose solutions.
> --
> cheers
> paul http://acm.org/~mpb
>
>
> _______________________________________________
> OpenAFS-info mailing list
> OpenAFS-info@openafs.org
> https://lists.openafs.org/mailman/listinfo/openafs-info
>
_______________________________________________
OpenAFS-info mailing list
OpenAFS-info@openafs.org
https://lists.openafs.org/mailman/listinfo/openafs-info
--=_alternative 0049C793C1256CD1_=
Content-Type: text/html; charset="US-ASCII"
<br><font size=2 face="sans-serif">hy , </font>
<br>
<br><font size=2 face="sans-serif">yes i know , under aix it is not a Problem
, but under Linux (Redhat 8.0 Kernel 2.4.18) </font>
<br>
<br><font size=2 face="sans-serif">Sven</font>
<br>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td>
<td><font size=1 face="sans-serif"><b>Paul Blackburn <mpb@est.ibm.com></b></font>
<br><font size=1 face="sans-serif">Sent by: openafs-info-admin@openafs.org</font>
<p><font size=1 face="sans-serif">02/18/2003 01:47 PM</font>
<td><font size=1 face="Arial"> </font>
<br><font size=1 face="sans-serif"> To:
Sven Oehme/Germany/IBM@IBMDE</font>
<br><font size=1 face="sans-serif"> cc:
Edward Moy <emoy@apple.com>, openafs-info@openafs.org,
openafs-info-admin@openafs.org</font>
<br><font size=1 face="sans-serif"> Subject:
Re: [OpenAFS] poor out of cache behavior
on writing</font>
<br>
<br><font size=1 face="Arial"> </font></table>
<br>
<br><font size=2><tt>Sven,<br>
I have seen that using a 256mb RAM cache on a machine with 1gb RAM<br>
running AIX did not crash.<br>
--<br>
cheers<br>
paul
http://acm.org/~mpb<br>
<br>
Sven Oehme wrote:<br>
<br>
><br>
> hy ,<br>
><br>
> i have seen increasing the memcache size >50 mb on a Linux Server
with <br>
> 512 mb that afs is crashing .<br>
><br>
> Sven<br>
><br>
><br>
><br>
><br>
> *Paul Blackburn <mpb@est.ibm.com>*<br>
> Sent by: openafs-info-admin@openafs.org<br>
><br>
> 02/18/2003 10:06 AM<br>
><br>
> <br>
> To: Edward
Moy <emoy@apple.com><br>
> cc: openafs-info@openafs.org<br>
> Subject: Re:
[OpenAFS] poor out of cache behavior on <br>
> writing<br>
><br>
> <br>
><br>
><br>
><br>
> Edward Moy wrote:<br>
><br>
> ><br>
> > Yes, it is true that fast read performance should be a higher<br>
> > priority. But if I want to read a 1 GB file from AFS, I have
to write<br>
> > it there in the first place.<br>
> ><br>
> > Look at the times to read that same 1 GB file:<br>
> ><br>
> > nfs 0.050u 18.050s 2:25.59 12.4%<br>
> > afs 0.5GB cache 0.030u 10.300s 2:29.26 6.9%<br>
> > afs 2GB cache 0.030u 11.250s 2:32.67 7.3%<br>
> ><br>
> > Within the normal fluctuations in the network itself, AFS is
very<br>
> > close to raw NFA, for first-time reading. But also note that
even when<br>
> > the cache is smaller than the file, one does not see the poor
behavior<br>
> > exhibited in the write case.<br>
><br>
> Hi Edward,<br>
><br>
> I think you have succintly made the point that you need to size<br>
> your AFS cache appropriately for your workload.<br>
><br>
> If you plan on working with 1gb files often and writing 1gb files<br>
> into /afs/@cell/$whatever/ then you better configure a big enough
AFS <br>
> cache.<br>
><br>
> I think that "cache thrashing" is similar to "page
thrashing"<br>
> in virtual memory operating systems. It is a situation that<br>
> occurs when there is not enough resource allocated (eg cache too small)<br>
> for the workload applied to it.<br>
><br>
> Remember also that with AFS, you have a choice of disk cache<br>
> or RAM cache. So if you have enough installed RAM, you<br>
> will see faster access using AFS RAM cache (than using disk cache).<br>
><br>
> ><br>
> ><br>
> > It takes 2 1/2 minutes to read the file, and 4 minutes to write
it<br>
> > when there is enough cache. But as a user, when that goes up
to 10<br>
> > minutes, and uses 80% of the processor, my first reaction would
be<br>
> > that something is wrong.<br>
> ><br>
> > From other comments I've seen, it appears that this is "expected"<br>
> > (though hopefully not desirable) behavior. I just wanted to point
out<br>
> > that there is room for improvement in this area.<br>
><br>
> You are absolutely right to point this out.<br>
> If there is something "not working right" with AFS write
function<br>
> then this is a good place to discuss it and propose solutions.<br>
> --<br>
> cheers<br>
> paul http://acm.org/~mpb<br>
><br>
><br>
> _______________________________________________<br>
> OpenAFS-info mailing list<br>
> OpenAFS-info@openafs.org<br>
> https://lists.openafs.org/mailman/listinfo/openafs-info<br>
><br>
<br>
<br>
<br>
_______________________________________________<br>
OpenAFS-info mailing list<br>
OpenAFS-info@openafs.org<br>
https://lists.openafs.org/mailman/listinfo/openafs-info<br>
</tt></font>
<br>
--=_alternative 0049C793C1256CD1_=--