================
@@ -216,6 +228,35 @@ u64 GetShadowCount(uptr p, u32 size) {
return count;
}
+// Accumulates the access count from the shadow for the given pointer and size.
+// See memprof_mapping.h for an overview on histogram counters.
+u64 GetShadowCountHistogram(uptr p, u32 size) {
+ u8 *shadow = (u8 *)HISTOGRAM_MEM_TO_SHADOW(p);
+ u8 *shadow_end = (u8 *)HISTOGRAM_MEM_TO_SHADOW(p + size);
+ u64 count = 0;
+ for (; shadow <= shadow_end; shadow++)
+ count += *shadow;
+ return count;
+}
+
+// If we use the normal approach from clearCountersWithoutHistogram, the
+// histogram will clear too much data and may overwrite shadow counters that
are
+// in use. Likely because of rounding up the shadow_end pointer.
+// See memprof_mapping.h for an overview on histogram counters.
+void clearCountersHistogram(uptr addr, uptr size) {
+ u8 *shadow_8 = (u8 *)HISTOGRAM_MEM_TO_SHADOW(addr);
+ u8 *shadow_end_8 = (u8 *)HISTOGRAM_MEM_TO_SHADOW(addr + size);
+ for (; shadow_8 < shadow_end_8; shadow_8++) {
+ *shadow_8 = 0;
+ }
+}
+
+void clearCountersWithoutHistogram(uptr addr, uptr size) {
+ uptr shadow_beg = MEM_TO_SHADOW(addr);
+ uptr shadow_end = MEM_TO_SHADOW(addr + size - SHADOW_GRANULARITY) + 1;
+ REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
+}
+
// Clears the shadow counters (when memory is allocated).
void ClearShadow(uptr addr, uptr size) {
----------------
teresajohnson wrote:
I guess it works, because the shadow granularities are less than the page size,
and because they are both scaling by the same 8 to 1 scale, and also I guess
because the clear_shadow_mmap_threshold is an optimization and doesn't need to
be exact. However, it still feels a little wonky to me (and also means that we
have to do extra mapping operations here and again in `clearCounters*`). I do
think I would prefer to have it be something like:
```
uptr shadow_beg;
uptr shadow_end;
if (__memprof_histogram) {
shadow_beg = HISTOGRAM_MEM_TO_SHADOW(addr);
shadow_end = HISTOGRAM_MEM_TO_SHADOW(addr + size);
} else {
shadow_beg = MEM_TO_SHADOW(addr);
shadow_end = MEM_TO_SHADOW(addr + size - SHADOW_GRANULARITY) + 1;
}
if (shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
} else {
...
```
I.e. set shadow_beg/end based on whether we are doing the histogramming or not,
leave the rest as-is. Would that work?
https://github.com/llvm/llvm-project/pull/94264
_______________________________________________
lldb-commits mailing list
lldb-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
