linux-kernel - Re: [PATCHv2 5/6] zsmalloc: extend compaction statistics

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Date:   Sun, 26 Feb 2023 12:55:45 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yosry Ahmed <yosryahmed@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv2 5/6] zsmalloc: extend compaction statistics

On (23/02/23 15:51), Minchan Kim wrote:
> On Thu, Feb 23, 2023 at 12:04:50PM +0900, Sergey Senozhatsky wrote:
> > Extend zsmalloc zs_pool_stats with a new member that
> > holds the number of objects pool compaction moved
> > between pool pages.
> 
> I totally understand this new stat would be very useful for your
> development but not sure it's really useful for workload tune or
> monitoring.
> 
> Unless we have strong usecase, I'd like to avoid new stat.

The way I see is that it *can* give some interesting additional data to
periodical compaction (the one is not triggeed by the shrinker): if the
number of moves objects is relatively high but the number of comapcted
(feeed) pages is relatively low then the system has fragmentation in
small size classes (that tend to have many objects per zspage but not
too many pages per zspage) and in this case the interval between
periodical compactions probably can be increased. What do you think?