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    SubjectRe: [PATCH 4/7] mm, vmscan: show LRU name in mm_vmscan_lru_isolate tracepoint
    On Thu 29-12-16 15:02:04, Minchan Kim wrote:
    > On Wed, Dec 28, 2016 at 04:30:29PM +0100, Michal Hocko wrote:
    > > From: Michal Hocko <mhocko@suse.com>
    > >
    > > mm_vmscan_lru_isolate currently prints only whether the LRU we isolate
    > > from is file or anonymous but we do not know which LRU this is. It is
    > > useful to know whether the list is file or anonymous as well. Change
    > > the tracepoint to show symbolic names of the lru rather.
    > >
    > > Signed-off-by: Michal Hocko <mhocko@suse.com>
    >
    > Not exactly same with this but idea is almost same.
    > I used almost same tracepoint to investigate agging(i.e., deactivating) problem
    > in 32b kernel with node-lru.
    > It was enough. Namely, I didn't need tracepoint in shrink_active_list like your
    > first patch.
    > Your first patch is more straightforwad and information. But as you introduced
    > this patch, I want to ask in here.
    > Isn't it enough with this patch without your first one to find a such problem?

    I assume this should be a reply to
    http://lkml.kernel.org/r/20161228153032.10821-8-mhocko@kernel.org, right?
    And you are right that for the particular problem it was enough to have
    a tracepoint inside inactive_list_is_low and shrink_active_list one
    wasn't really needed. On the other hand aging issues are really hard to
    debug as well and so I think that both are useful. The first one tell us
    _why_ we do aging while the later _how_ we do that.
    --
    Michal Hocko
    SUSE Labs

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