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Date:   Fri, 22 Nov 2019 18:33:25 -0800
From:   Matthew Wilcox <willy@infradead.org>
To:     "zhengbin (A)" <zhengbin13@huawei.com>
Cc:     Hugh Dickins <hughd@google.com>, viro@zeniv.linux.org.uk,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        houtao1@huawei.com, yi.zhang@huawei.com,
        "J. R. Okajima" <hooanon05g@gmail.com>,
        Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH] tmpfs: use ida to get inode number
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On Sat, Nov 23, 2019 at 10:16:39AM +0800, zhengbin (A) wrote:
> By the way, percpu IDA is for reducing performance impact? This patch has 2.16%
> performance degradation(Use perf to get the cost of ida_alloc_range)

2.16% degradation in your tests ... I bet Eric didn't make it so complex
for only 2% performance impact.  Unfortunately, he didn't give any
numbers in his patch submission, but it's going to be a bigger problem
on multi-socket machines than on a laptop.

Eric, any memories from 2010?  Commit
f991bd2e14210fb93d722cb23e54991de20e8a3d if it helps.