RE: [PATCH 1/1] selftest/net: fix FILE_SIZE for 32 bit architecture.

Hi,

On 08/02/2018 03:31 AM, Maninder Singh wrote:

quoted

FILE_SZ is defined as (1UL << 35), it will overflow
for 32 bit system and logic will break.

Signed-off-by: Maninder Singh <redacted>
Signed-off-by: Vaneet Narang <redacted>
---
 tools/testing/selftests/net/tcp_mmap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/net/tcp_mmap.c b/tools/testing/selftests/net/tcp_mmap.c
index e8c5dff..1d6ca12 100644
--- a/tools/testing/selftests/net/tcp_mmap.c
+++ b/tools/testing/selftests/net/tcp_mmap.c

@@ -85,7 +85,7 @@
 #define MSG_ZEROCOPY    0x4000000
 #endif
 
-#define FILE_SZ (1UL << 35)
+#define FILE_SZ (1ULL << 35)

...
...

quoted

@@ -431,7 +431,7 @@ int main(int argc, char *argv[])
                 zflg = 0;
         }
         while (total < FILE_SZ) {
-                long wr = FILE_SZ - total;
+                unsigned long long wr = FILE_SZ - total;
 
                 if (wr > chunk_size)
                         wr = chunk_size;

What about using more conventional size_t instead of "unsigned long long" ?

size_t is also equivalent to unsigned long and it will not hold value of (1 << 35) for 32 bit system.
So we can do two things.

(1) reduce FILE SIZE to (1 << 30), so that UL (size_t) can hold this value.
It will not show any perofrmance boost with ZEROCOPY. (checked on x86_64)

(2) use unsigned long long to work with both 32 and 64 bit system.
It will show performance boost with ZEROCOPY.(checked on x86_64)

What do you think?

Thanks and regards,
Maninder Singh