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    SubjectRe: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in direct reclaim
    On Thu, 14 Jul 2011 00:46:43 -0400
    Christoph Hellwig <hch@infradead.org> wrote:

    > On Thu, Jul 14, 2011 at 10:38:01AM +0900, KAMEZAWA Hiroyuki wrote:
    > > > + /*
    > > > + * Only kswapd can writeback filesystem pages to
    > > > + * avoid risk of stack overflow
    > > > + */
    > > > + if (page_is_file_cache(page) && !current_is_kswapd()) {
    > > > + inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
    > > > + goto keep_locked;
    > > > + }
    > > > +
    > >
    > >
    > > This will cause tons of memcg OOM kill because we have no help of kswapd (now).
    >
    > XFS and btrfs already disable writeback from memcg context, as does ext4
    > for the typical non-overwrite workloads, and none has fallen apart.
    >
    > In fact there's no way we can enable them as the memcg calling contexts
    > tend to have massive stack usage.
    >

    Hmm, XFS/btrfs adds pages to radix-tree in deep stack ?

    Thanks,
    -Kame



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