Re: mm, slab/slub: Ensure kmem_cache_alloc_bulk() is available early

[Thomas Gleixner]

On Tue, Feb 07 2023 at 15:47, Vlastimil Babka wrote:
> From 340d7c7b99f3e67780f6dec480ed1d27e6f325eb Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@xxxxxxx>
> Date: Tue, 7 Feb 2023 15:34:53 +0100
> Subject: [PATCH] mm, slab/slub: remove notes that bulk alloc/free needs
>  interrupts enabled
>
> The slab functions kmem_cache_[alloc|free]_bulk() have been documented
> as requiring interrupts to be enabled, since their addition in 2015.
> It's unclear whether that was a fundamental restriction, or an attempt
> to save some cpu cycles by not having to save and restore the irq
> flags.

I don't think so. The restriction is rather meant to avoid huge
allocations in atomic context which causes latencies and also might
deplete the atomic reserves.

So I rather avoid that and enforce !ATOMIC mode despite the
local_irq_save/restore() change which is really only to accomodate with
early boot.

Thanks,

        tglx