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// Copyright 2019 The TCMalloc Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "tcmalloc/internal/mincore.h"
#include <sys/mman.h>
#include <unistd.h>
#include <algorithm>
#include <cstdint>
#include "tcmalloc/internal/config.h"
GOOGLE_MALLOC_SECTION_BEGIN
namespace tcmalloc {
namespace tcmalloc_internal {
// Class that implements the call into the OS provided mincore() function.
class OsMInCore final : public MInCoreInterface {
public:
int mincore(void* addr, size_t length, unsigned char* result) final {
return ::mincore(addr, length, result);
}
~OsMInCore() override = default;
};
// Returns the number of resident bytes for an range of memory of arbitrary
// alignment and size.
size_t MInCore::residence_impl(void* addr, size_t size,
MInCoreInterface* mincore) {
if (size == 0) {
return 0;
}
unsigned char res[kArrayLength];
const size_t kPageSize = getpagesize();
uintptr_t uaddr = reinterpret_cast<uintptr_t>(addr);
// Round address down to get the start of the page containing the data.
uintptr_t basePage = uaddr & ~(kPageSize - 1);
// Round end address up to get the end of the page containing the data.
uintptr_t endPage = (uaddr + size + kPageSize - 1) & ~(kPageSize - 1);
uintptr_t remainingPages = endPage - basePage;
// We need to handle the first and last pages differently. Most pages
// will contribute pagesize bytes to residence, but the first and last
// pages will contribute fewer than that. Easiest way to do this is to
// handle the special case where the entire object fits into a page,
// then handle the case where the object spans more than one page.
if (remainingPages == kPageSize) {
// Find out whether the first page is resident.
mincore->mincore(reinterpret_cast<void*>(basePage), remainingPages, res);
// Residence info is returned in LSB, other bits are undefined.
if ((res[0] & 1) == 1) {
return size;
}
return 0;
}
// We're calling this outside the loop so that we can get info for the
// first page, deal with subsequent pages in the loop, and then handle
// the last page after the loop.
size_t scanLength = std::min(remainingPages, kPageSize * kArrayLength);
if (mincore->mincore(reinterpret_cast<void*>(basePage), scanLength, res) !=
0) {
return 0;
}
size_t totalResident = 0;
// Handle the first page.
size_t firstPageSize = kPageSize - (uaddr - basePage);
if ((res[0] & 1) == 1) {
totalResident += firstPageSize;
}
basePage += kPageSize;
remainingPages -= kPageSize;
int resIndex = 1;
// Handle all pages but the last page.
while (remainingPages > kPageSize) {
if ((res[resIndex] & 1) == 1) {
totalResident += kPageSize;
}
resIndex++;
basePage += kPageSize;
remainingPages -= kPageSize;
// Refresh the array if necessary.
if (resIndex == kArrayLength) {
resIndex = 0;
scanLength = std::min(remainingPages, kPageSize * kArrayLength);
if (mincore->mincore(reinterpret_cast<void*>(basePage), scanLength,
res) != 0) {
return 0;
}
}
}
// Check final page
size_t lastPageSize = kPageSize - (endPage - uaddr - size);
if ((res[resIndex] & 1) == 1) {
totalResident += lastPageSize;
}
return totalResident;
}
// Return residence info using call to OS provided mincore().
size_t MInCore::residence(void* addr, size_t size) {
OsMInCore mc;
return residence_impl(addr, size, &mc);
}
} // namespace tcmalloc_internal
} // namespace tcmalloc
GOOGLE_MALLOC_SECTION_END
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