From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Peter Zijlstra <peterz@infradead.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Mel Gorman <mgorman@techsingularity.net>,
Tony Luck <tony.luck@intel.com>, Vlastimil Babka <vbabka@suse.cz>,
Michal Hocko <mhocko@kernel.org>,
"hillf.zj" <hillf.zj@alibaba-inc.com>,
Hugh Dickins <hughd@google.com>, Oleg Nesterov <oleg@redhat.com>,
Rik van Riel <riel@redhat.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [mm 4.15-rc8] Random oopses under memory pressure.
Date: Sat, 20 Jan 2018 02:02:37 +0000 [thread overview]
Message-ID: <20180120020237.GM13338@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFw4mw32Mu0_+cgKAzxCNvDW1VPcESv7CyajexfDfMju1A@mail.gmail.com>
On Fri, Jan 19, 2018 at 02:53:25PM -0800, Linus Torvalds wrote:
> It would probably be good to add the size too, just to explain why
> it's potentially expensive.
>
> That said, apparently we do have hundreds of them, with just
> cpufreq_frequency_table having a ton. Maybe some are hidden in macros
> and removing one removes a lot.
cpufreq_table_find_index_...(), mostly.
> The real problem is that sometimes the subtraction is simply the right
> thing to do, and there's no sane way to say "yeah, this is one of
> those cases you shouldn't warn about".
FWIW, the sizes of the most common ones are
91 sizeof struct cpufreq_frequency_table = 12
Almost all of those come from
cpufreq_for_each_valid_entry(pos, table)
if (....)
return pos - table;
and I wonder if we would be better off with something like
#define cpufreq_for_each_valid_entry(pos, table, idx) \
for (pos = table, idx = 0; pos->frequency != CPUFREQ_TABLE_END; pos++, idx++) \
if (pos->frequency == CPUFREQ_ENTRY_INVALID) \
continue; \
else
so that those loops would become
cpufreq_for_each_valid_entry(pos, table, idx)
if (....)
return idx;
36 sizeof struct Indirect = 24
21 sizeof struct ips_scb = 216
18 sizeof struct runlist_element = 24
13 sizeof struct zone = 1728
Some are from
#define zone_idx(zone) ((zone) - (zone)->zone_pgdat->node_zones)
but there's
static inline int zone_id(const struct zone *zone)
{
struct pglist_data *pgdat = zone->zone_pgdat;
return zone - pgdat->node_zones;
}
and a couple of places where we have
for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
Those bloody well ought to be
for (zone = node_zones, end = node_zones + MAX_NR_ZONES; zone < end; zone++) {
13 sizeof struct vring = 40
11 sizeof struct usbhsh_device = 24
10 sizeof struct xpc_partition = 888
9 sizeof struct skge_element = 40
9 sizeof struct lock_class = 400
9 sizeof struct hstate = 29872
That little horror comes from get_hstate_idx() and hstate_index(). Code generated
for division is
movabsq $-5542915600080909725, %rax
sarq $4, %rdi
imulq %rdi, %rax
7 sizeof struct nvme_rdma_queue = 312
7 sizeof struct iso_context = 208
6 sizeof struct i915_power_well = 48
6 sizeof struct hpet_dev = 168
6 sizeof struct ext4_extent = 12
6 sizeof struct esas2r_target = 120
5 sizeof struct iio_chan_spec = 152
5 sizeof struct hwspinlock = 96
4 sizeof struct myri10ge_slice_state = 704
4 sizeof struct ext4_extent_idx = 12
Another interesting-looking one is struct vhost_net_virtqueue (18080 bytes)
Note that those sizes are rather sensitive to lockdep, spinlock debugging, etc.
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next prev parent reply other threads:[~2018-01-20 2:05 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-05 14:45 [x86? mm? fs? 4.15-rc6] Random oopses by simple write under memory pressure Tetsuo Handa
2018-01-09 10:39 ` [mm? 4.15-rc7] " Tetsuo Handa
2018-01-10 11:49 ` [mm? 4.15-rc7] Random oopses " Tetsuo Handa
2018-01-10 12:45 ` Michal Hocko
2018-01-10 13:37 ` Tetsuo Handa
2018-01-11 13:57 ` Michal Hocko
2018-01-11 14:11 ` Tetsuo Handa
2018-01-11 14:21 ` Michal Hocko
2018-01-11 14:37 ` Tetsuo Handa
2018-01-12 1:31 ` [mm " Tetsuo Handa
2018-01-12 1:42 ` Linus Torvalds
2018-01-12 11:22 ` Tetsuo Handa
2018-01-14 11:54 ` Tetsuo Handa
2018-01-15 23:05 ` Linus Torvalds
2018-01-16 1:15 ` [mm 4.15-rc8] " Tetsuo Handa
2018-01-16 2:14 ` Linus Torvalds
2018-01-16 8:06 ` Dave Hansen
2018-01-16 8:37 ` Ingo Molnar
2018-01-16 19:30 ` Linus Torvalds
2018-01-16 17:33 ` Tetsuo Handa
2018-01-16 19:34 ` Linus Torvalds
2018-01-17 11:08 ` Tetsuo Handa
2018-01-17 21:39 ` Linus Torvalds
2018-01-17 21:51 ` Linus Torvalds
2018-01-17 22:04 ` Dave Hansen
2018-01-17 22:00 ` Dave Hansen
2018-01-17 22:15 ` Linus Torvalds
2018-01-18 8:12 ` Tetsuo Handa
2018-01-18 12:25 ` Kirill A. Shutemov
2018-01-18 13:12 ` Kirill A. Shutemov
2018-01-18 14:34 ` Kirill A. Shutemov
2018-01-18 14:38 ` Dave Hansen
2018-01-18 14:45 ` Kirill A. Shutemov
2018-01-18 14:51 ` Dave Hansen
2018-01-18 16:58 ` Linus Torvalds
2018-01-18 14:45 ` Dave Hansen
2018-01-18 14:58 ` Andrea Arcangeli
2018-01-18 16:56 ` Kirill A. Shutemov
2018-01-18 17:26 ` Luck, Tony
2018-01-18 17:28 ` Linus Torvalds
2018-01-18 17:26 ` Linus Torvalds
2018-01-18 23:49 ` Kirill A. Shutemov
2018-01-19 12:55 ` Matthew Wilcox
2018-01-19 18:42 ` Linus Torvalds
2018-01-19 22:12 ` Al Viro
2018-01-19 22:53 ` Linus Torvalds
2018-01-20 2:02 ` Al Viro [this message]
2018-01-20 5:24 ` Al Viro
2018-01-20 9:38 ` Luc Van Oostenryck
2018-01-18 15:40 ` Kirill A. Shutemov
2018-01-18 17:22 ` Michal Hocko
2018-01-19 10:02 ` Kirill A. Shutemov
2018-01-19 10:33 ` Michal Hocko
2018-01-19 11:49 ` Kirill A. Shutemov
2018-01-19 12:07 ` Michal Hocko
2018-01-19 12:30 ` Kirill A. Shutemov
2018-01-19 2:01 ` Tetsuo Handa
2018-01-11 18:11 ` [mm? 4.15-rc7] " Linus Torvalds
2018-01-11 20:59 ` Tetsuo Handa
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