linux-kernel - Re: [PATCH] Change the total_dirty from SZ_256M to SZ

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Date:   Sat, 3 Nov 2018 11:01:14 +0200
From:   Nikolay Borisov <nborisov@...e.com>
To:     hmsjwzb <weizhefix@...il.com>
Cc:     clm@...com, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>,
        Omar Sandoval <osandov@...com>,
        Filipe Manana <fdmanana@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Change the total_dirty from SZ_256M to SZ_64M.



On 3.11.18 г. 10:36 ч., hmsjwzb wrote:
> The SZ_256M will cause trouble in platform with less than 256M memory.
> For example, a qemu virtual machine.
> 
> Signed-off-by: hmsjwzb <weizhefix@...il.com>

If you have actually taken the care to understand the code in
test_find_delalloc you would have seen that total_dirty and max_bytes
are actually inter-dependent so you cannot really change total_bytes
without adjusting max_bytes as well. Otherwise tests will start breaking.

NACK on this (and likely any future postings of this) since the tests
are sized in a such a way so as to test design limits (such as the max
extent size which is 128MB)


> ---
>  fs/btrfs/tests/extent-io-tests.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/tests/extent-io-tests.c b/fs/btrfs/tests/extent-io-tests.c
> index 9e0f4a01be14..cb23dce96a2d 100644
> --- a/fs/btrfs/tests/extent-io-tests.c
> +++ b/fs/btrfs/tests/extent-io-tests.c
> @@ -62,7 +62,7 @@ static int test_find_delalloc(u32 sectorsize)
>  	struct page *page;
>  	struct page *locked_page = NULL;
>  	unsigned long index = 0;
> -	u64 total_dirty = SZ_256M;
> +	u64 total_dirty = SZ_64M;
>  	u64 max_bytes = SZ_128M;
>  	u64 start, end, test_start;
>  	u64 found;
>