Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932539AbcJRHU2 (ORCPT ); Tue, 18 Oct 2016 03:20:28 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:4621 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754734AbcJRHUU (ORCPT ); Tue, 18 Oct 2016 03:20:20 -0400 From: To: CC: , , , , , , , , , , , , , , , , Subject: [PATCH] bdi flusher should not be throttled here when it fall into buddy slow path Date: Tue, 18 Oct 2016 15:12:45 +0800 Message-ID: <1476774765-21130-1-git-send-email-zhouxianrong@huawei.com> X-Mailer: git-send-email 1.7.9.5 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.143.155.56] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3266 Lines: 80 From: z00281421 bdi flusher may enter page alloc slow path due to writepage and kmalloc. in that case the flusher as a direct reclaimer should not be throttled here because it can not to reclaim clean file pages or anaonymous pages for next moment; furthermore writeback rate of dirty pages would be slow down and other direct reclaimers and kswapd would be affected. bdi flusher should be iosceduled by get_request rather than here. Signed-off-by: z00281421 --- fs/fs-writeback.c | 4 ++-- include/linux/sched.h | 1 + mm/vmscan.c | 15 +++++++++++---- 3 files changed, 14 insertions(+), 6 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 05713a5..f6bf067 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1908,7 +1908,7 @@ void wb_workfn(struct work_struct *work) long pages_written; set_worker_desc("flush-%s", dev_name(wb->bdi->dev)); - current->flags |= PF_SWAPWRITE; + current->flags |= (PF_SWAPWRITE | PF_BDI_FLUSHER | PF_LESS_THROTTLE); if (likely(!current_is_workqueue_rescuer() || !test_bit(WB_registered, &wb->state))) { @@ -1938,7 +1938,7 @@ void wb_workfn(struct work_struct *work) else if (wb_has_dirty_io(wb) && dirty_writeback_interval) wb_wakeup_delayed(wb); - current->flags &= ~PF_SWAPWRITE; + current->flags &= ~(PF_SWAPWRITE | PF_BDI_FLUSHER | PF_LESS_THROTTLE); } /* diff --git a/include/linux/sched.h b/include/linux/sched.h index 62c68e5..4bb70f2 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2232,6 +2232,7 @@ extern void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, #define PF_KTHREAD 0x00200000 /* I am a kernel thread */ #define PF_RANDOMIZE 0x00400000 /* randomize virtual address space */ #define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */ +#define PF_BDI_FLUSHER 0x01000000 /* I am bdi flusher */ #define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_allowed */ #define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */ #define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */ diff --git a/mm/vmscan.c b/mm/vmscan.c index 0fe8b71..492e9e7 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1643,12 +1643,19 @@ putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list) * If a kernel thread (such as nfsd for loop-back mounts) services * a backing device by writing to the page cache it sets PF_LESS_THROTTLE. * In that case we should only throttle if the backing device it is - * writing to is congested. In other cases it is safe to throttle. + * writing to is congested. another case is that bdi flusher could + * not be throttled here even though whose bdi is consgested. + * In other cases it is safe to throttle. */ -static int current_may_throttle(void) +static bool current_may_throttle(void) { - return !(current->flags & PF_LESS_THROTTLE) || - current->backing_dev_info == NULL || + if (!(current->flags & PF_LESS_THROTTLE)) + return true; + + if (current->flags & PF_BDI_FLUSHER) + return false; + + return current->backing_dev_info == NULL || bdi_write_congested(current->backing_dev_info); } -- 1.7.9.5