The "kmem -i" command is extremely slow (appears to hang) on dumps from large 
memory systems.

For example, on 120GB crash dump from a high-end server with 32TB of RAM (ie. 
8Giga Pages),
the "kmem -i" command is taking over 50 minutes to execute on a DL380 Gen10. To 
report basic
general memory usage figures, we should only be reading global counters, 
without having to walk
the full flat/sparse mem map page table. Hence, dump_kmeminfo() should first be 
reading globals,
and then only call dump_mem_map() if important information (ie. slabs or total 
ram) is missing.


Signed-off-by: Georges Aureau 
<georges.aur...@hpe.com<mailto:georges.aur...@hpe.com>>

--
diff --git a/memory.c b/memory.c
index 8c01ed0..8e2b2e9 100644
--- a/memory.c
+++ b/memory.c
@@ -8546,18 +8546,19 @@ dump_kmeminfo(void)
         ulong get_buffers;
         ulong get_slabs;
             char buf[BUFSIZE];
+            ulong flags;
-
-             BZERO(&meminfo, sizeof(struct meminfo));
-             meminfo.flags = GET_ALL;
-             dump_mem_map(&meminfo);
-             get_totalram = meminfo.get_totalram;
-             shared_pages = meminfo.get_shared;
-             get_buffers = meminfo.get_buffers;
-             get_slabs = meminfo.get_slabs;
+            /*
+            * By default, we will no longer call dump_mem_map() as this is too
+            * slow for large memory systems. If we have to call it (eg. missing
+            * important information such as slabs or total ram), we will also
+            * collect shared pages. Otherwise, we won't print shared pages.
+            */
+            flags = GET_SHARED_PAGES;
+            shared_pages = 0;
              /*
-             *  If vm_stat array exists, override page search info.
+            *  If vm_stat array does not exists, then set mem map flag.
              */
             if (vm_stat_init()) {
                            if (dump_vm_stat("NR_SLAB", &nr_slab, 0))
@@ -8571,10 +8572,11 @@ dump_kmeminfo(void)
                                          get_slabs = nr_slab;
                                          if 
(dump_vm_stat("NR_SLAB_UNRECLAIMABLE_B", &nr_slab, 0))
                                                         get_slabs += nr_slab;
+                           } else {
+                                         flags |= GET_SLAB_PAGES;
                            }
             }
-             fprintf(fp, "%s", kmeminfo_hdr);
             /*
              *  Get total RAM based upon how the various versions of 
si_meminfo()
          *  have done it, latest to earliest:
@@ -8586,9 +8588,32 @@ dump_kmeminfo(void)
                 symbol_exists("_totalram_pages")) {
                            totalram_pages = vt->totalram_pages ?
                                           vt->totalram_pages : get_totalram;
-             } else
-                           totalram_pages = get_totalram;
+            } else {
+                           flags |= GET_TOTALRAM_PAGES;
+            }
+            /*
+            * If we want more than just shared pages (missing slabs or total 
ram)
+            * then call dump_mem_map() and also collect buffers.
+            */
+            if (flags != GET_SHARED_PAGES) {
+                           BZERO(&meminfo, sizeof(struct meminfo));
+                           flags |= GET_BUFFERS_PAGES;
+                           meminfo.flags = flags;
+                           dump_mem_map(&meminfo);
+                           /* Update the missing information */
+                           if (flags & GET_SLAB_PAGES) {
+                                         get_slabs = meminfo.get_slabs;
+                           }
+                           if (flags & GET_TOTALRAM_PAGES) {
+                                         get_totalram = meminfo.get_totalram;
+                                         totalram_pages = get_totalram;
+                           }
+                           shared_pages = meminfo.get_shared;
+                           get_buffers = meminfo.get_buffers;
+            }
+
+            fprintf(fp, "%s", kmeminfo_hdr);
             fprintf(fp, "%13s  %7ld  %11s         ----\n", "TOTAL MEM",
                             totalram_pages, pages_to_size(totalram_pages, 
buf));
@@ -8613,9 +8638,11 @@ dump_kmeminfo(void)
          *  differently than the kernel -- it just tallies the non-reserved
          *  pages that have a count of greater than 1.
              */
-        pct = (shared_pages * 100)/totalram_pages;
-        fprintf(fp, "%13s  %7ld  %11s  %3ld%% of TOTAL MEM\n",
-                           "SHARED", shared_pages, pages_to_size(shared_pages, 
buf), pct);
+            if (shared_pages) {
+            pct = (shared_pages * 100)/totalram_pages;
+            fprintf(fp, "%13s  %7ld  %11s  %3ld%% of TOTAL MEM\n",
+                                         "SHARED", shared_pages, 
pages_to_size(shared_pages, buf), pct);
+            }
              subtract_buffer_pages = 0;
             if (symbol_exists("buffermem_pages")) {
@@ -8634,7 +8661,7 @@ dump_kmeminfo(void)
         fprintf(fp, "%13s  %7ld  %11s  %3ld%% of TOTAL MEM\n",
                             "BUFFERS", buffer_pages, 
pages_to_size(buffer_pages, buf), pct);
-             if (CRASHDEBUG(1))
+            if (CRASHDEBUG(1)&&(flags&GET_BUFFERS_PAGES))
              error(NOTE, "pages with buffers: %ld\n", get_buffers);
              /*

--
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