On Sun, 2007-07-22 at 18:33 +1000, Rusty Russell wrote:
> On Sun, 2007-07-22 at 16:10 +0800, Fengguang Wu wrote:
> > - It will avoid large-file-reads-thrashing-my-desktop problem,
> > so most desktop users should like it. But sure there will be counter
> > cases when a user want to keep the data cached.
> > - File servers may hurt from it. Imagine a mp3/png file server. The
> > files are large enough to trigger drop-behind, but small (and hot)
> > enough to be cached. Also when a new fedora DVD iso is released, it
> > may be cached for some days. These are only the obvious cases.
>
> I'm still not convinced of the latter case. If a second user accesses
> the file before it pages are thrown out, from my understanding there
> won't be readahead but the pages will be put back on the active list
> (ie. the dropbehind is undone).
>
> AFAICT this patch truly biasses towards releasing pages from
> sequentially accessed files. So file servers where memory pressure
> comes from lots of such files should be fine (bias will work correctly
> against least-served files).
>
> The main problem I can see is a low-memory server where we are currently
> swapping out pages from non-sequential files (eg. gigantic running java
> apps), and now performance might decline because we'll discard file
> pages first.
>
> > So I opt for it being made tunable, safe, and turned off by default.
>
> I'd like to see it turned on by default in -mm, and try to come up with
> some server-like workload to measure the effect. Should be easy to
> simulate something (eg. apache server, where clients grab some files in
> preference, and apache server where clients grab different files).
>
> Peter?
I guess we could do that. Just populate the server with a lot of
randomly sized files, and make a client do a random pull or one with a
poisson distribution or something like that.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
