Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Wed, 28 Feb 2024 15:14:04 -0800 | From | Tony Luck <> | Subject | [PATCH] x86/mce: Dynamically size space for machine check records |
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Systems with a large number of CPUs may generate a large number of machine check records when things go seriously wrong. But Linux has a fixed buffer that can only capture a few dozen errors.
Allocate space based on the number of CPUs (with a minimum value based on the historical fixed buffer that could store 80 records).
Signed-off-by: Tony Luck <tony.luck@intel.com> ---
Discussion earlier concluded with the realization that it is safe to dynamically allocate the mce_evt_pool at boot time. So here's a patch to do that. Scaling algorithm here is a simple linear "4 records per possible CPU" with a minimum of 80 to match the legacy behavior. I'm open to other suggestions.
Note that I threw in a "+1" to the return from ilog2() when calling gen_pool_create(). From reading code, and running some tests, it appears that the min_alloc_order argument needs to be large enough to allocate one of the mce_evt_llist structures.
Some other gen_pool users in Linux may also need this "+1".
arch/x86/kernel/cpu/mce/genpool.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/cpu/mce/genpool.c b/arch/x86/kernel/cpu/mce/genpool.c index fbe8b61c3413..a1f0a8f29cf5 100644 --- a/arch/x86/kernel/cpu/mce/genpool.c +++ b/arch/x86/kernel/cpu/mce/genpool.c @@ -16,14 +16,13 @@ * used to save error information organized in a lock-less list. * * This memory pool is only to be used to save MCE records in MCE context. - * MCE events are rare, so a fixed size memory pool should be enough. Use - * 2 pages to save MCE events for now (~80 MCE records at most). + * MCE events are rare, so a fixed size memory pool should be enough. + * Allocate on a sliding scale based on number of CPUs. */ -#define MCE_POOLSZ (2 * PAGE_SIZE) +#define MCE_MIN_ENTRIES 80 static struct gen_pool *mce_evt_pool; static LLIST_HEAD(mce_event_llist); -static char gen_pool_buf[MCE_POOLSZ]; /* * Compare the record "t" with each of the records on list "l" to see if @@ -118,14 +117,25 @@ int mce_gen_pool_add(struct mce *mce) static int mce_gen_pool_create(void) { + int mce_numrecords, mce_poolsz; struct gen_pool *tmpp; int ret = -ENOMEM; + void *mce_pool; + int order; - tmpp = gen_pool_create(ilog2(sizeof(struct mce_evt_llist)), -1); + order = ilog2(sizeof(struct mce_evt_llist)) + 1; + tmpp = gen_pool_create(order, -1); if (!tmpp) goto out; - ret = gen_pool_add(tmpp, (unsigned long)gen_pool_buf, MCE_POOLSZ, -1); + mce_numrecords = max(80, num_possible_cpus() * 4); + mce_poolsz = mce_numrecords * (1 << order); + mce_pool = kmalloc(mce_poolsz, GFP_KERNEL); + if (!mce_pool) { + gen_pool_destroy(tmpp); + goto out; + } + ret = gen_pool_add(tmpp, (unsigned long)mce_pool, mce_poolsz, -1); if (ret) { gen_pool_destroy(tmpp); goto out; -- 2.43.0
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