Sri Lanka have wrestled back momentum in the second Test against Australia, going to stumps on day two at 2-184 in reply to Australia's 364.

Sri Lanka have rediscovered their fight amid the chaos of protests in Galle to put themselves back in the second Test against Australia.

After rolling through Australia's tail and leaving Steve Smith unbeaten on 145, Sri Lanka went to stumps on day two at 2-184 in response to Australia's 364.

Captain Dimuth Karunaratne led the charge with 86, combining with Kusal Mendis (84 not out) for Sri Lanka's biggest second-wicket partnership against Australia.

It came on a dramatic day at Galle's International Stadium, with thousands protesting outside the ground and the nation's president fleeing his palace 125km away in Colombo.

The demonstration has left cricket something of a sideshow after months of economic crisis in the country.

But on the field, the home side put up a much-needed resistance in their best day of the series so far.

Bowled out in 22.5 overs last week, Sri Lanka lost just two wickets in almost triple that time on Saturday.

Karunaratne also scored double the runs he did during Australia's last tour, after struggling through the three-Test series in 2016.

Destroyed by Mitchell Starc six years ago, the opener played the Australian paceman well despite being roughed up once by a short ball from the left-armer.

He survived chances on 18 and 35, through a run-out and a Mitchell Swepson caught-and-bowled.

Swepson eventually got his man when a delivery skidded on and trapped the left-hander lbw.

Nevertheless, the skipper set the tone in the 152-run stand with Mendis, who pulled and hooked Pat Cummins effectively among 19 boundaries.

What's also undeniable is that this wicket has far less venom than the one Sri Lanka were bowled out for 113 on a week ago.

Reverse-swing has also been hard to come by, with Australia having the ball changed twice without extracting movement.

Starc was the only pace bowler to have success, drawing Pathum Nissanka's edge on six when he angled a ball across the right-hander.

Still, Australia know the wicket will deteriorate and Mendis needs to match Smith in the scoring stakes to help his team avoid a series loss.

Australia have made it clear they are prepared to play the long game, much in the same way they did in Pakistan earlier this year on more batter-friendly wickets.

"There's not as much reverse swing as Pakistan. The square's probably a bit greener, a bit more lush," Smith said.

"The spin is probably going to play more of a part.

"(The wicket) is probably not too dissimilar to last time we were here where the skidding balls have probably been more dangerous than the spinning one.

"They are still a fair way away from our score ... and we have the liberty of not having to bat last."

Smith had rarely looked challenged on day one or day two after bringing up his first century in exactly 18 months on Friday.

When he and Alex Carey resumed at 5-298 on Saturday, it appeared as if Australia could build an imposing total.

But after Carey reverse-swept Prabath Jayasuriya to deep point on 28, Australia's tail of Starc, Cummins, Nathan Lyon and Swepson could only muster 14 runs between them.

Jayasuriya's figures of 6-118 were also the second best by a Sri Lankan on Test debut after he also got the key wicket of century-maker Marnus Labuschagne on Friday.