From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id F3D096B0035 for ; Thu, 21 Aug 2014 09:05:27 -0400 (EDT) Received: by mail-pa0-f51.google.com with SMTP id ey11so14076203pad.24 for ; Thu, 21 Aug 2014 06:05:27 -0700 (PDT) Received: from mail-pa0-x236.google.com (mail-pa0-x236.google.com [2607:f8b0:400e:c03::236]) by mx.google.com with ESMTPS id of4si36395102pdb.243.2014.08.21.06.05.26 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 21 Aug 2014 06:05:26 -0700 (PDT) Received: by mail-pa0-f54.google.com with SMTP id fa1so14691835pad.27 for ; Thu, 21 Aug 2014 06:05:26 -0700 (PDT) Date: Thu, 21 Aug 2014 22:05:04 +0900 From: Sergey Senozhatsky Subject: Re: [PATCH] zram: add num_discards for discarded pages stat Message-ID: <20140821130504.GB946@swordfish> References: <001201cfb838$fb0ac4a0$f1204de0$@samsung.com> <20140815061138.GA940@swordfish> <002d01cfbb70$ea7410c0$bf5c3240$@samsung.com> <20140819112500.GA2484@swordfish> <20140820020924.GD32620@bbox> <006701cfbc4f$c9d2fe00$5d78fa00$@samsung.com> <20140821011854.GE17372@bbox> <001601cfbd1f$b9f068d0$2dd13a70$@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <001601cfbd1f$b9f068d0$2dd13a70$@samsung.com> Sender: owner-linux-mm@kvack.org List-ID: To: Chao Yu Cc: 'Minchan Kim' , 'Sergey Senozhatsky' , linux-kernel@vger.kernel.org, linux-mm@kvack.org, ngupta@vflare.org, 'Jerome Marchand' , 'Andrew Morton' On (08/21/14 17:09), Chao Yu wrote: [cut] > > > > I hope I'm not discouraging. :) > > Nope, please let me try again, :) > > Since we have supported handling discard request in this commit > f4659d8e620d08bd1a84a8aec5d2f5294a242764 (zram: support REQ_DISCARD), zram got > one more chance to free unused memory whenever received discard request. But > without stating for discard request, there is no method for user to know whether > discard request has been handled by zram or how many blocks were discarded by > zram when user wants to know the effect of discard. > > In this patch, we add num_discards to stat discarded pages, and export it to > sysfs for users. > In other words, here is my proposal: -----8<-----8<----- Subject: [PATCH] zram: use notify_free to account all free notifications notify_free device attribute accounts the number of slot free notifications and internally represents the number of zram_free_page() calls. Slot free notifications are sent only when device is used as a swap device, hence notify_free is used only for swap devices. Since f4659d8e620d08 (zram: support REQ_DISCARD) ZRAM handles yet another one free notification (also via zram_free_page() call) -- REQ_DISCARD requests, which are sent by a filesystem, whenever some data blocks are discarded. However, there is no way to know the number of notifications in the latter case. Use notify_free to account the number of pages freed in zram_free_page(), instead of accounting only swap_slot_free_notify() calls (each zram_slot_free_notify() call frees one page). This means that depending on usage scenario notify_free represents: a) the number of pages freed because of slot free notifications, which is equal to the number of swap_slot_free_notify() calls, so there is no behaviour change b) the number of pages freed because of REQ_DISCARD notifications Signed-off-by: Sergey Senozhatsky --- Documentation/ABI/testing/sysfs-block-zram | 13 ++++++++----- drivers/block/zram/zram_drv.c | 2 +- 2 files changed, 9 insertions(+), 6 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram index 70ec992..73ed400 100644 --- a/Documentation/ABI/testing/sysfs-block-zram +++ b/Documentation/ABI/testing/sysfs-block-zram @@ -77,11 +77,14 @@ What: /sys/block/zram/notify_free Date: August 2010 Contact: Nitin Gupta Description: - The notify_free file is read-only and specifies the number of - swap slot free notifications received by this device. These - notifications are sent to a swap block device when a swap slot - is freed. This statistic is applicable only when this disk is - being used as a swap disk. + The notify_free file is read-only. Depending on device usage + scenario it may account a) the number of swap slot free + notifications or b) the number of REQ_DISCARD requests sent + by bio. The former ones are sent to a swap block device when a + swap slot is freed, which implies that this disk is being used + as a swap disk. The latter ones are sent by filesystem mounted + with discard option, whenever some data blocks are getting + discarded. What: /sys/block/zram/zero_pages Date: August 2010 diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index d00831c..c2e7127 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -344,6 +344,7 @@ static void zram_free_page(struct zram *zram, size_t index) atomic64_sub(zram_get_obj_size(meta, index), &zram->stats.compr_data_size); atomic64_dec(&zram->stats.pages_stored); + atomic64_inc(&zram->stats.notify_free); meta->table[index].handle = 0; zram_set_obj_size(meta, index, 0); @@ -843,7 +844,6 @@ static void zram_slot_free_notify(struct block_device *bdev, bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value); zram_free_page(zram, index); bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value); - atomic64_inc(&zram->stats.notify_free); } static const struct block_device_operations zram_devops = { -- 2.1.0.233.g9eef2c8 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org