linux-kernel - Re: [PATCH] mm/page-writeback: Raise wb_thresh to prevent write blocking with strictlimit

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Message-Id: <20241023162447.2bf480b4ce590fdeb8b6c52d@linux-foundation.org>
Date: Wed, 23 Oct 2024 16:24:47 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jim Zhao <jimzhao.ai@...il.com>
Cc: willy@...radead.org, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/page-writeback: Raise wb_thresh to prevent write
 blocking with strictlimit

On Wed, 23 Oct 2024 18:00:32 +0800 Jim Zhao <jimzhao.ai@...il.com> wrote:

> With the strictlimit flag, wb_thresh acts as a hard limit in
> balance_dirty_pages() and wb_position_ratio(). When device write
> operations are inactive, wb_thresh can drop to 0, causing writes to
> be blocked. The issue occasionally occurs in fuse fs, particularly
> with network backends, the write thread is blocked frequently during
> a period. To address it, this patch raises the minimum wb_thresh to a
> controllable level, similar to the non-strictlimit case.

Please tell us more about the userspace-visible effects of this.  It
*sounds* like a serious (but occasional) problem, but that is unclear.

And, very much relatedly, do you feel this fix is needed in earlier
(-stable) kernels?