On Wed, 2 Jul 2014 09:13:46 +0900 Minchan Kim <minc...@kernel.org> wrote:
> Normally, I/O completed pages for reclaim would be rotated into > inactive LRU tail without freeing. The why it works is we can't free > page from atomic context(ie, end_page_writeback) due to vaious locks > isn't aware of atomic context. > > So for reclaiming the I/O completed pages, we need one more iteration > of reclaim and it could make unnecessary aging as well as CPU overhead. > > Long time ago, at the first trial, most concern was memcg locking > but recently, Johnannes tried amazing effort to make memcg lock simple > and got merged into mmotm so I coded up based on mmotm tree. > (Kudos to Johannes) > > On 1G, 12 CPU kvm guest, build kernel 5 times and result was > > allocstall > vanilla: records: 5 avg: 4733.80 std: 913.55(19.30%) max: 6442.00 min: 3719.00 > improve: records: 5 avg: 1514.20 std: 441.69(29.17%) max: 1974.00 min: 863.00 Well yes. We're now doing unaccounted, impact-a-random-process work in irq context which was previously being done in process context, accounted to the process which was allocating the memory. Some would call this a regression ;) > pgrotated > vanilla: records: 5 avg: 873313.80 std: 40999.20(4.69%) max: 954722.00 min: > 845903.00 > improve: records: 5 avg: 28406.40 std: 3296.02(11.60%) max: 34552.00 min: > 25047.00 Still a surprisingly high amount of rotation going on. > Most of field in vmstat are not changed too much but things I can notice > is allocstall and pgrotated. We could save allocstall(ie, direct relcaim) > and pgrotated very much. > > Welcome testing, review and any feedback! Well, it will worsen IRQ latencies and it's all more code for us to maintain. I think I'd like to see a better story about the end-user benefits before proceeding. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
