From: Andi Kleen <ak@muc.de>
To: Kanoj Sarcar <kanoj@google.engr.sgi.com>
Cc: linux-mm@kvack.org, torvalds@transmeta.com
Subject: Re: Some issues + [PATCH] kanoj-mm8-2.2.9 Show statistics on alloc/free requests for each pagefree list
Date: Sat, 12 Jun 1999 12:21:07 +0200 [thread overview]
Message-ID: <19990612122107.A2245@fred.muc.de> (raw)
In-Reply-To: <199906120102.SAA64168@google.engr.sgi.com>; from Kanoj Sarcar on Sat, Jun 12, 1999 at 03:02:18AM +0200
On Sat, Jun 12, 1999 at 03:02:18AM +0200, Kanoj Sarcar wrote:
> Anyway, this raises some interesting questions about the buddy algorithm.
> Is it really worth aggressively coalescing pages on each free? Wouldn't
> it be better to lazily coalesce pages (maybe by a kernel thread), or even
> on demand? By far, the most number of requests are coming for the 4K pages,
> followed by 8K (task/stack pair). A kernel compile is no representative
> app, but I would be surprised if there are too many apps/drivers which
> will force bigger page requests, once kernel initialization is complete.
> Wouldn't it be better to optimize the more common case?
There is a important case ATM that needs bigger blocks allocated from
bottom half context: NFS packet defragmenting. For a 8K wsize it needs
even 16K blocks (8K payload + the IP/UDP header forces it to the next
buddy size). I guess your statistics would look very different on a nfsroot
machine. Until lazy defragmenting is supported for UDP it is probably
better not to change it.
-Andi
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next prev parent reply other threads:[~1999-06-12 10:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-06-12 1:02 Some issues + [PATCH] kanoj-mm8-2.2.9 Show statistics on alloc/free requests for each pagefree list Kanoj Sarcar
1999-06-12 10:21 ` Andi Kleen [this message]
1999-06-14 17:34 ` Kanoj Sarcar
1999-06-14 16:45 ` Andi Kleen
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