[PATCH] D141659: [BOLT][HUGIFY] Adds fix for -hugify option

[Alexey Moksyakov via Phabricator via llvm-commits]

yavtuk updated this revision to Diff 490388.
yavtuk edited the summary of this revision.
yavtuk added a comment.

@maksfb how about such kind of checking? we can check the files in runtime and based on it check one of way


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D141659/new/

https://reviews.llvm.org/D141659

Files:
  bolt/runtime/hugify.cpp


Index: bolt/runtime/hugify.cpp
===================================================================
--- bolt/runtime/hugify.cpp
+++ bolt/runtime/hugify.cpp
@@ -60,7 +60,7 @@
 
 /// Check whether the kernel supports THP via corresponding sysfs entry.
 /// thp works only starting from 5.10
-static bool hasPagecacheTHPSupport() {
+static bool isTHPEnabled() {
   char Buf[64];
 
   int FD = __open("/sys/kernel/mm/transparent_hugepage/enabled",
@@ -68,7 +68,7 @@
   if (FD < 0)
     return false;
 
-  memset(Buf, 0, sizeof(Buf));
+  Buf[0] = '\0';
   const size_t Res = __read(FD, Buf, sizeof(Buf));
   if (Res < 0)
     return false;
@@ -76,6 +76,10 @@
   if (!strStr(Buf, "[always]") && !strStr(Buf, "[madvise]"))
     return false;
 
+  return true;
+}
+
+static bool isKernelSupportTHP() {
   struct KernelVersionTy {
     uint32_t major;
     uint32_t minor;
@@ -85,8 +89,36 @@
   KernelVersionTy KernelVersion;
 
   getKernelVersion((uint32_t *)&KernelVersion);
-  if (KernelVersion.major >= 5 && KernelVersion.minor >= 10)
-    return true;
+  if (KernelVersion.major < 5 || KernelVersion.minor < 10)
+    return false;
+
+  int FD = __open("/boot/config", 0 /* O_RDONLY */, 0);
+  if (FD < 0)
+    return false;
+
+  char Buf[128];
+  char ch;
+  uint64_t i = 0;
+  const uint64_t num = sizeof("CONFIG_");
+  void *pRes;
+  Buf[0] = '\0';
+  while(__read(FD, Buf, num) > 0) {
+    i = num;
+    while (__read(FD, &ch, 1) > 0 && ch != '\n')
+      Buf[i++] = ch;
+
+    pRes = strStr(Buf, "CONFIG_READ_ONLY_THP_FOR_FS");
+    if (pRes) {
+      // OFF: # CONFIG_READ_ONLY_THP_FOR_FS is not
+      //  ON: CONFIG_READ_ONLY_THP_FOR_FS=y
+      DEBUG(report(Buf));
+      const char *p = (char *)pRes + sizeof("CONFIG_READ_ONLY_THP_FOR_FS");
+      if (*p == 'y')
+        return true;
+      return false;
+    }
+    Buf[0] = '\0';
+  }
 
   return false;
 }
@@ -150,13 +182,18 @@
   DEBUG(reportNumber("[hugify] aligned huge page from: ", (uint64_t)From, 16);)
   DEBUG(reportNumber("[hugify] aligned huge page to: ", (uint64_t)To, 16);)
 
-  if (!hasPagecacheTHPSupport()) {
+  if (!isTHPEnabled()) {
     DEBUG(report(
-              "[hugify] workaround with memory alignment for kernel < 5.10\n");)
-    hugifyForOldKernel(From, To);
+          "[hugify] THP is disabled, please check /sys/kernel/mm/transparent_hugepage/enabled\n");)
     return;
   }
 
+  if (!isKernelSupportTHP()) {
+    DEBUG(report(
+          "[hugify] workaround with memory alignment for kernel < 5.10\n");)
+    hugifyForOldKernel(From, To);
+  }
+
   if (__madvise(From, (To - From), 14 /* MADV_HUGEPAGE */) == -1) {
     char Msg[] = "[hugify] failed to allocate large page\n";
     // TODO: allow user to control the failure behavior.


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