On Sat, Sep 4, 2010 at 11:04 AM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote: > On Sat, Sep 04, 2010 at 08:02:27AM +0800, Andrew Morton wrote: >> On Thu, 2 Sep 2010 23:34:47 +0900 >> Minchan Kim <minchan.kim@xxxxxxxxx> wrote: >> >> > Now update_nr_listpages doesn't have a role. That's because >> > lists passed is always empty just after calling migrate_pages. >> > The migrate_pages cleans up page list which have failed to migrate >> > before returning by aaa994b3. >> > >> > [PATCH] page migration: handle freeing of pages in migrate_pages() >> > >> > Do not leave pages on the lists passed to migrate_pages(). Seems that we will >> > not need any postprocessing of pages. This will simplify the handling of >> > pages by the callers of migrate_pages(). >> > >> > At that time, we thought we don't need any postprocessing of pages. >> > But the situation is changed. The compaction need to know the number of >> > failed to migrate for COMPACTPAGEFAILED stat >> > >> > This patch makes new rule for caller of migrate_pages to call putback_lru_pages. >> > So caller need to clean up the lists so it has a chance to postprocess the pages. >> > [suggested by Christoph Lameter] >> >> I'm having trouble predicting what the user-visible effects of this bug >> might be. Just an inaccuracy in the COMPACTPAGEFAILED vm event? > > Right, it's an accounting fix. Before patch COMPACTPAGEFAILED will > remain 0 regardless of how many migration failures. > > The patch does slightly add dependency for migrate_pages() to return > error code properly. Before patch, migrate_pages() calls > putback_lru_pages() regardless of the error code. After patch, the > migrate_pages() callers will check its return value before calling > putback_lru_pages(). > > In current code, the two conditions do seem to match: > > "some pages remained in the *from list" == "migrate_pages() returns an error code". Exactly. Thanks for the answering instead of me, Wu. :) > Thanks, > Fengguang > -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href