[Crash-utility] [PATCH v3] Speed up "kmem -[sS]" by optimizing is_page_ptr() for x86_64
Dave Anderson
anderson at redhat.com
Tue Mar 6 16:27:44 UTC 2018
Hi Kazuhito,
Looks good -- queued for crash-7.2.2:
https://github.com/crash-utility/crash/commit/4141373d9de3fea29f5d2b58f60e44bc132726c0
Thanks,
Dave
----- Original Message -----
> changes v2 -> v3:
> - move the setting point of machdep->is_page_ptr to machdep_init(SETUP_ENV)
> changes v1 -> v2:
> - rewrite based on the per-architecture function call Dave provided
> - remove the part which used page.flags for non-VMEMMAP kernels
> - add address range/position check first
> - remove/optimize the calculations of mem_map and phys address
> - modify the patch description
>
> The "kmem -[sS]" commands can take several minutes to complete with
> the following conditions:
> - The system has a lot of memory sections with CONFIG_SPARSEMEM, and
> - The kernel uses SLUB and it has a very long partial slab list.
>
> crash> kmem -s dentry
> CACHE NAME OBJSIZE ALLOCATED TOTAL SLABS
> SSIZE
> ffff88017fc78a00 dentry 192 9038949 10045728 239184
> 8k
> crash> kmem -s dentry | bash -c 'cat >/dev/null ; echo $SECONDS'
> 133
> crash> kmem -S dentry | bash -c 'cat >/dev/null ; echo $SECONDS'
> 656
>
> One of the causes is that is_page_ptr() in count_partial() determines
> whether a given slub page address is a page struct by searching all
> mem_sections available for the one which includes it.
>
> With CONFIG_SPARSEMEM_VMEMMAP on x86_64, we can do that by checking
> its address range and whether its calculated mem_section is valid.
> With this patch, the computation amount can be significantly reduced
> in that case.
>
> crash> kmem -s dentry | bash -c 'cat >/dev/null ; echo $SECONDS'
> 1
> crash> kmem -S dentry | bash -c 'cat >/dev/null ; echo $SECONDS'
> 1
>
> Signed-off-by: Kazuhito Hagio <k-hagio at ab.jp.nec.com>
> ---
> defs.h | 1 +
> x86_64.c | 23 +++++++++++++++++++++++
> 2 files changed, 24 insertions(+)
>
> diff --git a/defs.h b/defs.h
> index 9663bd8..7998ebf 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -5133,6 +5133,7 @@ int vaddr_type(ulong, struct task_context *);
> char *format_stack_entry(struct bt_info *bt, char *, ulong, ulong);
> int in_user_stack(ulong, ulong);
> int dump_inode_page(ulong);
> +ulong valid_section_nr(ulong);
>
>
> /*
> diff --git a/x86_64.c b/x86_64.c
> index 7449571..0d5e150 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -77,6 +77,7 @@ static void x86_64_calc_phys_base(void);
> static int x86_64_is_module_addr(ulong);
> static int x86_64_is_kvaddr(ulong);
> static int x86_64_is_uvaddr(ulong, struct task_context *);
> +static int x86_64_is_page_ptr(ulong, physaddr_t *);
> static ulong *x86_64_kpgd_offset(ulong, int, int);
> static ulong x86_64_upgd_offset(struct task_context *, ulong, int, int);
> static ulong x86_64_upgd_offset_legacy(struct task_context *, ulong, int,
> int);
> @@ -156,6 +157,7 @@ x86_64_init(int when)
> {
> case SETUP_ENV:
> machdep->process_elf_notes = x86_process_elf_notes;
> + machdep->is_page_ptr = x86_64_is_page_ptr;
> break;
> case PRE_SYMTAB:
> machdep->verify_symbol = x86_64_verify_symbol;
> @@ -802,6 +804,7 @@ x86_64_dump_machdep_table(ulong arg)
> fprintf(fp, " get_smp_cpus: x86_64_get_smp_cpus()\n");
> fprintf(fp, " is_kvaddr: x86_64_is_kvaddr()\n");
> fprintf(fp, " is_uvaddr: x86_64_is_uvaddr()\n");
> + fprintf(fp, " is_page_ptr: x86_64_is_page_ptr()\n");
> fprintf(fp, " verify_paddr: x86_64_verify_paddr()\n");
> fprintf(fp, " get_kvaddr_ranges: x86_64_get_kvaddr_ranges()\n");
> fprintf(fp, " init_kernel_pgd: x86_64_init_kernel_pgd()\n");
> @@ -1594,6 +1597,26 @@ x86_64_is_uvaddr(ulong addr, struct task_context *tc)
> return (addr < USERSPACE_TOP);
> }
>
> +static int
> +x86_64_is_page_ptr(ulong addr, physaddr_t *phys)
> +{
> + ulong pfn, nr;
> +
> + if (IS_SPARSEMEM() && (machdep->flags & VMEMMAP) &&
> + (addr >= VMEMMAP_VADDR && addr <= VMEMMAP_END) &&
> + !((addr - VMEMMAP_VADDR) % SIZE(page))) {
> +
> + pfn = (addr - VMEMMAP_VADDR) / SIZE(page);
> + nr = pfn_to_section_nr(pfn);
> + if (valid_section_nr(nr)) {
> + if (phys)
> + *phys = PTOB(pfn);
> + return TRUE;
> + }
> + }
> + return FALSE;
> +}
> +
> /*
> * Find the kernel pgd entry..
> * pgd = pgd_offset_k(addr);
> --
> 1.8.3.1
>
> --
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