From: Tejun Heo <tj@kernel.org>
To: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: willy@infradead.org, akpm@linux-foundation.org,
hcochran@kernelspring.com, mszeredi@redhat.com, axboe@kernel.dk,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/5] mm: correct calculation of cgroup wb's bg_thresh in wb_over_bg_thresh
Date: Tue, 23 Jan 2024 10:43:28 -1000 [thread overview]
Message-ID: <ZbAk8HfnzHoSSFWC@slm.duckdns.org> (raw)
In-Reply-To: <20240123183332.876854-3-shikemeng@huaweicloud.com>
On Wed, Jan 24, 2024 at 02:33:29AM +0800, Kemeng Shi wrote:
> The wb_calc_thresh will calculate wb's share in global wb domain. We need
> to wb's share in mem_cgroup_wb_domain for mdtc. Call __wb_calc_thresh
> instead of wb_calc_thresh to fix this.
That function is calculating the wb's portion of wb portion in the whole
system so that threshold can be distributed accordingly. So, it has to be
compared in the global domain. If you look at the comment on top of struct
wb_domain, it says:
/*
* A wb_domain represents a domain that wb's (bdi_writeback's) belong to
* and are measured against each other in. There always is one global
* domain, global_wb_domain, that every wb in the system is a member of.
* This allows measuring the relative bandwidth of each wb to distribute
* dirtyable memory accordingly.
*/
Also, how is this tested? Was there a case where the existing code
misbehaved that's improved by this patch? Or is this just from reading code?
Thanks.
--
tejun
next prev parent reply other threads:[~2024-01-23 20:43 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-23 18:33 [PATCH 0/5] Fix and cleanups to page-writeback Kemeng Shi
2024-01-23 18:33 ` [PATCH 1/5] mm: enable __wb_calc_thresh to calculate dirty background threshold Kemeng Shi
2024-01-23 18:33 ` [PATCH 2/5] mm: correct calculation of cgroup wb's bg_thresh in wb_over_bg_thresh Kemeng Shi
2024-01-23 20:43 ` Tejun Heo [this message]
2024-01-24 2:01 ` Kemeng Shi
2024-01-29 21:00 ` Tejun Heo
2024-02-08 9:26 ` Kemeng Shi
2024-02-08 19:32 ` Tejun Heo
2024-02-18 2:35 ` Kemeng Shi
2024-02-20 17:34 ` Tejun Heo
2024-01-23 18:33 ` [PATCH 3/5] mm: call __wb_calc_thresh instead of wb_calc_thresh " Kemeng Shi
2024-01-23 18:33 ` [PATCH 4/5] mm: remove redundant check in wb_min_max_ratio Kemeng Shi
2024-01-23 18:33 ` [PATCH 5/5] mm: remove stale comment __folio_mark_dirty Kemeng Shi
2024-01-23 14:07 ` Matthew Wilcox
2024-01-23 20:46 ` [PATCH 0/5] Fix and cleanups to page-writeback Tejun Heo
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