>> Unfortunately this part of the code is undergoing a lot of change >> lately. How serious is this problem? Please tell us how often the >> problem is being observed, under what circumstances, etc. > I have observed some problems in process-TIF_32BIT, such as Wechat > and others Android APP. > In the above processes which the single largest remaining free-addr-space > is 12Mbytes in some case, we found that the processes wound fail to alloc > a 12Mbytes(align 1M) in the old methods so that Out-of-Memory. > The idea of this patch is the same as the following patch which is used for > unmapped_area_topdown, as follows: > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/mm/mmap.c?id=5c6c46912cc0182fadd4b5f0eab029ccbbcc1ba3 ; > Thank you very much indeed to ask such nice question and I wish I have given > a clear reply. Pls let me know If there are any problems you found. Hi Andrew Morton： Pls help to review the patch and can it be merged into next-line? Thanks very much. lipeifeng@xxxxxxxx From: lipeifeng@xxxxxxxx Date: 2022-04-21 10:20 To: akpm CC: peifeng55; linux-mm; linux-kernel; Barry Song; zhangshiming Subject: Re: Re: [PATCH] mm: modify the method to search addr in unmapped_area Hi Andrew Morton： > Unfortunately this part of the code is undergoing a lot of change > lately. How serious is this problem? Please tell us how often the > problem is being observed, under what circumstances, etc. I have observed some problems in process-TIF_32BIT, such as Wechat and others Android APP. In the above processes which the single largest remaining free-addr-space is 12Mbytes in some case, we found that the processes wound fail to alloc a 12Mbytes(align 1M) in the old methods so that Out-of-Memory. The idea of this patch is the same as the following patch which is used for unmapped_area_topdown, as follows: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/mm/mmap.c?id=5c6c46912cc0182fadd4b5f0eab029ccbbcc1ba3 ; Thank you very much indeed to ask such nice question and I wish I have given a clear reply. Pls let me know If there are any problems you found. lipeifeng@xxxxxxxx From: Andrew Morton Date: 2022-04-21 05:57 To: lipeifeng CC: peifeng55; linux-mm; linux-kernel; 21cnbao; zhangshiming Subject: Re: [PATCH] mm: modify the method to search addr in unmapped_area On Wed, 20 Apr 2022 16:40:39 +0800 lipeifeng@xxxxxxxx wrote: > The old method will firstly find the space in len(info->length > + info->align_mask), and get address at the desired alignment. > > Sometime, addr would be failed if there are enough > addr space in kernel by above method, e.g., you can't get a > addr sized in 1Mbytes, align_mask 1Mbytes successfully although > there are still (2M-1)bytes space in kernel. > > This patch would fix thr problem above by the new method: find the > space in info->length and judge if at the desired info->align_mask > at the same time. > > Do a simple test in TIF_32BIT with unmapped_area: > - Try to take addr (size:1M align:2M) until allocation fails; > - Try to take addr (size:1M align:1M) and account how to space can > be alloced successfully. > > Before optimization: alloced 0 bytes. > After optimization: alloced 1.9+G bytes. Thanks. Unfortunately this part of the code is undergoing a lot of change lately. How serious is this problem? Please tell us how often the problem is being observed, under what circumstances, etc.
