Re: [PATCH v2] kmem: Add support to -S option to specify a range of CPU-specific slab data

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> Date: Tue, 13 Jul 2021 14:24:49 +0100
> From: Aaron Tomlin <atomlin@xxxxxxxxxx>
> To: crash-utility@xxxxxxxxxx
> Cc: k-haio-ab@xxxxxxx
> Subject:  [PATCH v2] kmem: Add support to -S option to
>         specify a range of CPU-specific slab data
> Message-ID: <20210713132449.2843627-1-atomlin@xxxxxxxxxx>
> Content-Type: text/plain; charset="US-ASCII"
>
> With this patch, it is now possible for one to explicitly specify a range
> of CPU-specific slab data to list. For example:
>
> Note: This is only applicable to a Linux kernel with Kconfig
>       CONFIG_SLUB enabled. The optional argument GNU extension
>       for getopt(3) is utilised; and, the CPU range must be
>       specified as expected
>
>     crash> kmem -S=1,4 kmalloc-512
>     CACHE             OBJSIZE  ALLOCATED     TOTAL  SLABS  SSIZE  NAME
>     ffff8d3f07c06c00      512       1916      3680    115    16k  kmalloc-512
>     CPU 1 KMEM_CACHE_CPU:
>       ffff8d461fa6f140
>     CPU 1 SLAB:
>       SLAB              MEMORY            NODE  TOTAL  ALLOCATED  FREE
>       fffff540df7c4000  ffff8d45df100000     0     32          8    24
>       FREE / [ALLOCATED]
>        ffff8d45df100000  (cpu 1 cache)
>       [ffff8d45df100200]
>        ffff8d45df100400  (cpu 1 cache)
>       [ffff8d45df100600]
>        ffff8d45df100800  (cpu 1 cache)
>        ffff8d45df100a00  (cpu 1 cache)
>        ffff8d45df100c00  (cpu 1 cache)
>        ffff8d45df100e00  (cpu 1 cache)
>        ffff8d45df101000  (cpu 1 cache)
>       [ffff8d45df101200]
>      ...skipped ...
>     CPU 4 KMEM_CACHE_CPU:
>       ffff8d461fb2f140
>     CPU 4 SLAB:
>       SLAB              MEMORY            NODE  TOTAL  ALLOCATED  FREE
>       fffff540dfde3800  ffff8d45f78e0000     0     32          8    24
>       FREE / [ALLOCATED]
>       [ffff8d45f78e0000]
>        ffff8d45f78e0200  (cpu 4 cache)
>        ffff8d45f78e0400  (cpu 4 cache)
>       [ffff8d45f78e0600]
>        ffff8d45f78e0800  (cpu 4 cache)
>        ffff8d45f78e0a00  (cpu 4 cache)
>        ffff8d45f78e0c00  (cpu 4 cache)
>        ffff8d45f78e0e00  (cpu 4 cache)
>        ffff8d45f78e1000  (cpu 4 cache)
>        ffff8d45f78e1200  (cpu 4 cache)
>        ffff8d45f78e1400  (cpu 4 cache)
>       [ffff8d45f78e1600]
>      ...skipped ...
>
> Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxx>
> ---
> Changes since v1:
>
>   - Do not explicitly exclude an offline CPU
>     as this is handled via hide_offline_cpu()
>     logic (Kazu)
>
> ---
>  help.c   |  5 ++++-
>  memory.c | 41 ++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 42 insertions(+), 4 deletions(-)
>
> diff --git a/help.c b/help.c
> index 99be7cb..6c262a3 100644
> --- a/help.c
> +++ b/help.c
> @@ -6601,7 +6601,7 @@ char *help_kmem[] = {
>  "kmem",
>  "kernel memory",
>  "[-f|-F|-c|-C|-i|-v|-V|-n|-z|-o|-h] [-p | -m member[,member]]\n"
> -"       [[-s|-S|-r] [slab] [-I slab[,slab]]] [-g [flags]] [[-P] address]]",
> +"       [[-s|-S|-S=cpu[s]|-r] [slab] [-I slab[,slab]]] [-g [flags]] [[-P] address]]",
>  "  This command displays information about the use of kernel memory.\n",
>  "        -f  displays the contents of the system free memory headers.",
>  "            also verifies that the page count equals nr_free_pages.",
> @@ -6649,6 +6649,9 @@ char *help_kmem[] = {
>  "            slab data for each per-cpu slab is displayed, along with the",
>  "            address of each kmem_cache_node, its count of full and partial",
>  "            slabs, and a list of all tracked slabs.",
> +"            Note: one can specify the per-cpu slab data to be displayed;",
> +"            the cpu[s] can be given as \"1,3,5\", \"1-3\", \"1,3,5-7,10\",",
> +"            \"all\", or \"a\" (shortcut for \"all\").",
>  "        -r  displays the accumulated basic kmalloc() slab data of each",
>  "            root slab cache and its children.  The kernel must contain the",
>  "            \"slab_root_caches\" list_head. (currently only available if",
> diff --git a/memory.c b/memory.c
> index cbe90ee..d59784c 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -48,6 +48,7 @@ struct meminfo {           /* general purpose memory information structure */
>         int slab_offset;
>          char *reqname;
>         char *curname;
> +       ulong *spec_cpumask;
>         ulong *addrlist;
>         int *kmem_bufctl;
>         ulong *cpudata[NR_CPUS];
> @@ -4851,10 +4852,13 @@ cmd_kmem(void)
>         struct meminfo meminfo;
>         ulonglong value[MAXARGS];
>         char buf[BUFSIZE];
> +       char arg_buf[BUFSIZE];
>         char *p1;
> -       int spec_addr, escape;
> +       ulong *cpus;
> +       int spec_addr, escape, choose_cpu;
>
> -       spec_addr = 0;
> +       cpus = NULL;
> +       spec_addr = choose_cpu = 0;
>          sflag =        Sflag = pflag = fflag = Fflag = Pflag = zflag = oflag = 0;
>         vflag = Cflag = cflag = iflag = nflag = lflag = Lflag = Vflag = 0;
>         gflag = hflag = rflag = 0;
> @@ -4863,7 +4867,7 @@ cmd_kmem(void)
>         BZERO(&value[0], sizeof(ulonglong)*MAXARGS);
>         pc->curcmd_flags &= ~HEADER_PRINTED;
>
> -        while ((c = getopt(argcnt, args, "gI:sSrFfm:pvczCinl:L:PVoh")) != EOF) {
> +        while ((c = getopt(argcnt, args, "gI:sS::rFfm:pvczCinl:L:PVoh")) != EOF) {
>                  switch(c)
>                 {
>                 case 'V':
> @@ -4903,6 +4907,33 @@ cmd_kmem(void)
>                         break;
>
>                 case 'S':
> +                       if (choose_cpu)
> +                               error(FATAL, "only one -S option allowed\n");
> +                       /* Use the GNU extension with getopt(3) ... */
> +                       if (optarg) {
> +                               if (!(vt->flags & KMALLOC_SLUB))
> +                                       error(FATAL,
> +                                               "can only use -S=cpu(s) with a kernel \n"
> +                                               "that is built with CONFIG_SLUB support.\n");
> +                               if (optarg[0] != '=')
> +                                       error(FATAL,
> +                                               "CPU-specific slab data to be displayed "
> +                                               "must be written as expected only e.g. -S=1,45.\n");
> +                               /* Skip = ... */
> +                               optarg++;
> +
> +                               choose_cpu = 1;
> +                               BZERO(arg_buf, BUFSIZE);
> +                               strcpy(arg_buf, optarg);
> +
> +                               cpus = get_cpumask_buf();
> +                               make_cpumask(arg_buf, cpus, FAULT_ON_ERROR, NULL);
> +                               meminfo.spec_cpumask = cpus;
> +
> +                               for (i = 0; i < kt->cpus; i++)
> +                                       if (NUM_IN_BITMAP(cpus, i) && check_offline_cpu(i))
> +                                               error(INFO, "CPU %d is OFFLINE.\n", i);
> +                       }
>                         Sflag = 1; sflag = rflag = 0;
>                         break;
>
> @@ -5185,6 +5216,8 @@ cmd_kmem(void)
>                         meminfo.flags = VERBOSE;
>                         vt->dump_kmem_cache(&meminfo);
>                 }
> +               if (choose_cpu)
> +                       FREEBUF(cpus);
>         }
>
>         if (vflag == 1)
> @@ -19083,6 +19116,8 @@ do_kmem_cache_slub(struct meminfo *si)
>         per_cpu = (ulong *)GETBUF(sizeof(ulong) * vt->numnodes);
>
>          for (i = 0; i < kt->cpus; i++) {
> +               if (si->spec_cpumask && !NUM_IN_BITMAP(si->spec_cpumask, i))
> +                       continue;
>                 if (hide_offline_cpu(i)) {
>                         fprintf(fp, "CPU %d [OFFLINE]\n", i);
>                         continue;
> --
> 2.31.1

For the v2 with Kazu's correction:
Acked-by: Lianbo Jiang <lijiang@xxxxxxxxxx>

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