linux-kernel - [PATCH 0/6] perf: Reduce stack usage (and misc bits)

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Message-ID: <20201030151345.540479897@infradead.org>
Date:   Fri, 30 Oct 2020 16:13:45 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     mingo@...nel.org, tglx@...utronix.de, rostedt@...dmis.org
Cc:     linux-kernel@...r.kernel.org, kan.liang@...ux.intel.com,
        acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, ak@...ux.intel.com, eranian@...gle.com,
        peterz@...radead.org
Subject: [PATCH 0/6] perf: Reduce stack usage (and misc bits)

Hi,

Steve reported an NMI stack overflow when running perf and function tracing
together. Thomas found that we had 4 copies of struct perf_sample_data
on-stack.

These here patches reduce that to 2 copies and half the size of it.

So just for perf_sample_data we go from 4*384=1536 to 2*192=384 bytes of stack.
Also remove one struct pt_regs instance from __intel_pmu_pebs_event(); it has
another instance in struct x86_perf_regs which I haven't yet managed to
offload.

Perf seems to still work... :-)