linux-kernel - Re: [PATCH v8 1/4] vmalloc: Add __vmalloc_node_try

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Message-Id: <20181106130511.9ebeb5a09aba15dfee2f7f3d@linux-foundation.org>
Date:   Tue, 6 Nov 2018 13:05:11 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc:     jeyu@...nel.org, willy@...radead.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-hardening@...ts.openwall.com, daniel@...earbox.net,
        jannh@...gle.com, keescook@...omium.org, kristen@...ux.intel.com,
        dave.hansen@...el.com, arjan@...ux.intel.com
Subject: Re: [PATCH v8 1/4] vmalloc: Add __vmalloc_node_try_addr function

On Fri,  2 Nov 2018 12:25:17 -0700 Rick Edgecombe <rick.p.edgecombe@...el.com> wrote:

> Create __vmalloc_node_try_addr function that tries to allocate at a specific
> address without triggering any lazy purging. In order to support this behavior
> a try_addr argument was plugged into several of the static helpers.

Please explain (in the changelog) why lazy purging is considered to be
a problem.  Preferably with some form of measurements, or at least a
hand-wavy guesstimate of the cost.

> This also changes logic in __get_vm_area_node to be faster in cases where
> allocations fail due to no space, which is a lot more common when trying
> specific addresses.