From: "tip-bot2 for Nadav Amit" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Nadav Amit <namit@vmware.com>, Ingo Molnar <mingo@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: x86/mm] x86/mm/tlb: Open-code on_each_cpu_cond_mask() for tlb_is_not_lazy()
Date: Sat, 06 Mar 2021 12:12:55 -0000 [thread overview]
Message-ID: <161503277583.398.13273853210620378454.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210220231712.2475218-4-namit@vmware.com>
The following commit has been merged into the x86/mm branch of tip:
Commit-ID: 6035152d8eebe16a5bb60398d3e05dc7799067b0
Gitweb: https://git.kernel.org/tip/6035152d8eebe16a5bb60398d3e05dc7799067b0
Author: Nadav Amit <namit@vmware.com>
AuthorDate: Sat, 20 Feb 2021 15:17:06 -08:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 06 Mar 2021 12:59:09 +01:00
x86/mm/tlb: Open-code on_each_cpu_cond_mask() for tlb_is_not_lazy()
Open-code on_each_cpu_cond_mask() in native_flush_tlb_others() to
optimize the code. Open-coding eliminates the need for the indirect branch
that is used to call is_lazy(), and in CPUs that are vulnerable to
Spectre v2, it eliminates the retpoline. In addition, it allows to use a
preallocated cpumask to compute the CPUs that should be.
This would later allow us not to adapt on_each_cpu_cond_mask() to
support local and remote functions.
Note that calling tlb_is_not_lazy() for every CPU that needs to be
flushed, as done in native_flush_tlb_multi() might look ugly, but it is
equivalent to what is currently done in on_each_cpu_cond_mask().
Actually, native_flush_tlb_multi() does it more efficiently since it
avoids using an indirect branch for the matter.
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20210220231712.2475218-4-namit@vmware.com
---
arch/x86/mm/tlb.c | 37 ++++++++++++++++++++++++++++++++-----
1 file changed, 32 insertions(+), 5 deletions(-)
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index bf12371..07b6701 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -788,11 +788,13 @@ done:
nr_invalidate);
}
-static bool tlb_is_not_lazy(int cpu, void *data)
+static bool tlb_is_not_lazy(int cpu)
{
return !per_cpu(cpu_tlbstate.is_lazy, cpu);
}
+static DEFINE_PER_CPU(cpumask_t, flush_tlb_mask);
+
STATIC_NOPV void native_flush_tlb_others(const struct cpumask *cpumask,
const struct flush_tlb_info *info)
{
@@ -813,12 +815,37 @@ STATIC_NOPV void native_flush_tlb_others(const struct cpumask *cpumask,
* up on the new contents of what used to be page tables, while
* doing a speculative memory access.
*/
- if (info->freed_tables)
+ if (info->freed_tables) {
smp_call_function_many(cpumask, flush_tlb_func,
(void *)info, 1);
- else
- on_each_cpu_cond_mask(tlb_is_not_lazy, flush_tlb_func,
- (void *)info, 1, cpumask);
+ } else {
+ /*
+ * Although we could have used on_each_cpu_cond_mask(),
+ * open-coding it has performance advantages, as it eliminates
+ * the need for indirect calls or retpolines. In addition, it
+ * allows to use a designated cpumask for evaluating the
+ * condition, instead of allocating one.
+ *
+ * This code works under the assumption that there are no nested
+ * TLB flushes, an assumption that is already made in
+ * flush_tlb_mm_range().
+ *
+ * cond_cpumask is logically a stack-local variable, but it is
+ * more efficient to have it off the stack and not to allocate
+ * it on demand. Preemption is disabled and this code is
+ * non-reentrant.
+ */
+ struct cpumask *cond_cpumask = this_cpu_ptr(&flush_tlb_mask);
+ int cpu;
+
+ cpumask_clear(cond_cpumask);
+
+ for_each_cpu(cpu, cpumask) {
+ if (tlb_is_not_lazy(cpu))
+ __cpumask_set_cpu(cpu, cond_cpumask);
+ }
+ smp_call_function_many(cond_cpumask, flush_tlb_func, (void *)info, 1);
+ }
}
void flush_tlb_others(const struct cpumask *cpumask,
next prev parent reply other threads:[~2021-03-06 12:14 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-20 23:17 [PATCH v6 0/9] x86/tlb: Concurrent TLB flushes Nadav Amit
2021-02-20 23:17 ` [PATCH v6 1/9] smp: Run functions concurrently in smp_call_function_many_cond() Nadav Amit
2021-03-01 17:10 ` Peter Zijlstra
2021-03-01 19:01 ` Nadav Amit
2021-03-02 7:05 ` [PATCH] smp: Micro-optimize smp_call_function_many_cond() Ingo Molnar
2021-03-02 9:54 ` [tip: x86/mm] smp: Run functions concurrently in smp_call_function_many_cond() tip-bot2 for Nadav Amit
2021-03-06 12:12 ` tip-bot2 for Nadav Amit
2021-02-20 23:17 ` [PATCH v6 2/9] x86/mm/tlb: Unify flush_tlb_func_local() and flush_tlb_func_remote() Nadav Amit
2021-03-02 9:54 ` [tip: x86/mm] " tip-bot2 for Nadav Amit
2021-03-06 12:12 ` tip-bot2 for Nadav Amit
2021-02-20 23:17 ` [PATCH v6 3/9] x86/mm/tlb: Open-code on_each_cpu_cond_mask() for tlb_is_not_lazy() Nadav Amit
2021-03-02 9:54 ` [tip: x86/mm] " tip-bot2 for Nadav Amit
2021-03-06 12:12 ` tip-bot2 for Nadav Amit [this message]
2021-02-20 23:17 ` [PATCH v6 4/9] x86/mm/tlb: Flush remote and local TLBs concurrently Nadav Amit
2021-03-02 9:54 ` [tip: x86/mm] " tip-bot2 for Nadav Amit
2021-03-06 12:12 ` tip-bot2 for Nadav Amit
2021-02-20 23:17 ` [PATCH v6 5/9] x86/mm/tlb: Privatize cpu_tlbstate Nadav Amit
2021-03-02 9:54 ` [tip: x86/mm] " tip-bot2 for Nadav Amit
2021-03-06 12:12 ` tip-bot2 for Nadav Amit
2021-02-20 23:17 ` [PATCH v6 6/9] x86/mm/tlb: Do not make is_lazy dirty for no reason Nadav Amit
2021-03-02 9:54 ` [tip: x86/mm] " tip-bot2 for Nadav Amit
2021-03-06 12:12 ` tip-bot2 for Nadav Amit
2021-02-20 23:17 ` [PATCH v6 7/9] cpumask: Mark functions as pure Nadav Amit
2021-03-02 9:54 ` [tip: x86/mm] " tip-bot2 for Nadav Amit
2021-03-06 12:12 ` tip-bot2 for Nadav Amit
2021-02-20 23:17 ` [PATCH v6 8/9] x86/mm/tlb: Remove unnecessary uses of the inline keyword Nadav Amit
2021-03-02 9:54 ` [tip: x86/mm] " tip-bot2 for Nadav Amit
2021-03-06 12:12 ` tip-bot2 for Nadav Amit
2021-02-20 23:17 ` [PATCH v6 9/9] smp: inline on_each_cpu_cond() and on_each_cpu() Nadav Amit
2021-03-02 9:54 ` [tip: x86/mm] smp: Inline " tip-bot2 for Nadav Amit
2021-03-06 12:12 ` tip-bot2 for Nadav Amit
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=161503277583.398.13273853210620378454.tip-bot2@tip-bot2 \
--to=tip-bot2@linutronix.de \
--cc=dave.hansen@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=namit@vmware.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).