linux-kernel - Re: [PATCH 5/6] riscv: allow kmalloc() caches aligned to the smallest value

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Message-ID: <ZHdfHgF3KO2PO/M2@xhacker>
Date:   Wed, 31 May 2023 22:52:14 +0800
From:   Jisheng Zhang <jszhang@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Conor Dooley <conor.dooley@...rochip.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] riscv: allow kmalloc() caches aligned to the
 smallest value

On Tue, May 30, 2023 at 02:08:10PM +0100, Catalin Marinas wrote:
> On Tue, May 30, 2023 at 11:34:06AM +0100, Conor Dooley wrote:
> > On Tue, May 30, 2023 at 10:59:41AM +0100, Catalin Marinas wrote:
> > > On Mon, May 29, 2023 at 12:17:46PM +0100, Conor Dooley wrote:
> > > > On Sat, May 27, 2023 at 12:59:57AM +0800, Jisheng Zhang wrote:
> > > > > After this patch, a simple test of booting to a small buildroot rootfs
> > > > > on qemu shows:
> > > > > 
> > > > > kmalloc-96           5041    5041     96  ...
> > > > > kmalloc-64           9606    9606     64  ...
> > > > > kmalloc-32           5128    5128     32  ...
> > > > > kmalloc-16           7682    7682     16  ...
> > > > > kmalloc-8           10246   10246      8  ...
> > > > > 
> > > > > So we save about 1268KB memory. The saving will be much larger in normal
> > > > > OS env on real HW platforms.
> > > > > 
> > > > > [1] Link: https://lore.kernel.org/linux-arm-kernel/20230524171904.3967031-1-catalin.marinas@arm.com/
> > 
> > While I think of it, Link: goes at the start of the line, the [1] should
> > go at the end (although I don't think you actually reference the link
> > anywhere in the text & it'll probably not be particularly relevant if a
> > subsequent revision of that patchset is applied.
> 
> I plan to post at least one more. I'd suggest the risc-v patchset to
> only go in once my series landed.

Sure I will wait for your series landing in linus tree firstly.

> 
> > > > > Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> > > > 
> > > > Fails to build chief, with loads of:
> > > > linux/dma-mapping.h:546:19: error: redefinition of 'dma_get_cache_alignment'
> > > > 
> > > > And for 32-bit there's also a rake of:
> > > > include/linux/slab.h:239:9: warning: 'ARCH_KMALLOC_MINALIGN' macro redefined [-Wmacro-redefined]
> > > > 
> > > > At the very least, reproducable with rv32_defconfig.
> > > 
> > > Have you this it on top of the KMALLOC_MINALIGN preparation series?
> > > 
> > > https://lore.kernel.org/r/20230524171904.3967031-1-catalin.marinas@arm.com/
> > 
> > Oh, no. Thanks for pointing that out.
> > Our automation stuff only uses what is in riscv/{for-next,master,fixes}.
> > Unless my reading comprehension is particularly bad of late it was

Aha I dunno this mechanism before.

> > non-obvious that this depended on something that had not yet been

Your reading comprehension is good ;) I just listed the dependency but
didn't explictly mention its merge status.

I will wait for Catalin's series being merged.